Dr Rajiv Desai

An Educational Blog

ELECTRICITY

 

ELECTRICITY:

_


The picture above shows how a barber cuts hair during recent power failure in India.

_

Prologue:

Electric crematoria were snuffed out with bodies inside, New Delhi’s Metro shut down and hundreds of coal miners were trapped underground after three Indian electric grids collapsed in a cascade on 30th and 31st July 2012, cutting power to 620 million people in India. The blackout engulfed as many as 19 of India’s 28 states on July 31, with more than 100 intercity trains stranded and traffic lights went out in busy roads, causing widespread jams. Without question, it was the largest blackout in world history. Hospitals, factories and the airports switched automatically to their diesel generators during the hours-long cut across half of India. Many homes relied on backup systems of invertors with batteries. On the other hand, millions of India’s poorest had no electricity to lose. Of the 1.5 billion people of the world who have no access to electricity in the world, India accounts for over 300 million. Humans have an intimate relationship with electricity, to the point that it’s virtually impossible to separate your life from it. Electricity figures everywhere in our lives. Electricity lights up our homes, cooks our food, powers our computers, television sets, and other electronic devices. Electricity from batteries keeps our cars running and makes our flashlights shine in the dark. Electricity is an extremely flexible form of energy, and it may be adapted to a huge and growing number of uses. Demand for electricity grows with great rapidity as a nation modernizes and its economy develops. The cost of electricity is going up (both in dollars and in environmental and health impacts) and it doesn’t show any signs of doing otherwise. Sure, you can flee from the world of crisscrossing power lines and live your life completely off the grid, but even at the loneliest corners of the world, electricity exists. If it’s not lighting up the storm clouds overhead or crackling in a static spark at your fingertips, then it’s moving through the human nervous system, animating the brain’s will in every flourish and through unthinking heartbeat. Yet, because we don’t actually see the electricity moving through, most people have only a vague idea of what the electricity is. This lack of intuition, of the “common sense” about a subject that comes from everyday familiarity – can be a problem when students first begin to try to understand electricity. So I decided to write on electricity taking inspiration from India’s perennial power outages for students and common people to understand electricity.  

_

Abbreviations, synonyms and formulas:

AC = alternating current

DC = direct current

BTU = British thermal unit = 1000 joules

EMF = electromotive force

EM waves = electromagnetic waves

_


_

Electricity is the flow of electrical power or charge. It is both a basic part of nature and one of our most widely used forms of energy. Electricity is actually a secondary energy source, also referred to as an energy carrier. That means that we get electricity from the conversion of other sources of energy, such as fossil fuel (coal, oil and natural gas), nuclear, hydropower, wind power or solar energy. These are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but electricity itself is neither renewable nor nonrenewable. The total worldwide annual primary energy consumption in 2008 was 435 quadrillion BTUs. Approximately 40 percent of the total primary energy is used in generating electricity. Of that, nearly 70 percent of the energy used in private homes and offices is in the form of electricity. Electricity is the most widely used and rapidly growing form of secondary energy supply. It offers great flexibility of distribution and use, is relatively efficient, very safe for the consumer, and environmentally benign in end-use. Before electricity became available over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves. However, even today, an estimated 79 percent of the people in the Third World from the 50 poorest nations have no access to electricity, despite decades of international development work. The total number of individuals without electric power is put at about 1.5 billion, or a quarter of the world’s population, concentrated mostly in Africa and southern Asia. With no electricity, many people in Third World countries cook their food over wood or coal burning. Replacing wood and coal with electricity could help reduce poverty and pollution.

_


_

Definition of electricity:

Electricity is the science, engineering, technology and physical phenomena associated with the presence and flow of electric charges. Electricity gives a wide variety of well-known electrical effects, such as lightning, static electricity, electromagnetic induction and the flow of electrical current in an electrical wire. In addition, electricity permits the creation and reception of electromagnetic radiation such as radio waves. The word electricity is from the New Latin ēlectricus, “amber-like”, coined in the year 1600 from the Greek word meaning amber, because electrical effects were produced classically by rubbing amber.

_

Electricity vis-à-vis electronics:

In electrical engineering, electricity is used for electric power (which can refer imprecisely to a quantity of electrical potential energy or else more correctly to electrical energy per time) that is provided commercially, by the electrical power industry. In a loose but common use of the term, “electricity” may be used to mean “wired for electricity” which means a working connection to an electric power station. Such a connection grants the user of “electricity” access to the electric field present in electrical wiring, and thus to electric power. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. Electricity is the domain of motors, light bulbs, generators, and other “large scale” items while Electronics is the domain of vacuum tubes, transistors, integrated circuits, and other “small scale” items.

_

Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical power supply. It now covers a range of subtopics including power, electronics, control systems, signal processing and telecommunications. Electrical engineering may include electronic engineering. Where a distinction is made, usually outside of the United States, electrical engineering is considered to deal with the problems associated with large-scale electrical systems such as power transmission and motor control, whereas electronic engineering deals with the study of small-scale electronic systems including computers and integrated circuits. Alternatively, electrical engineers are usually concerned with using electricity to transmit energy, while electronic engineers are concerned with using electricity to process information. Electric has to do with the general concept of electricity. In contrast, electronic is a term that is descriptive of devices that are powered by electricity. An electronic device is often constructed using one or more electric elements that make it possible to manage the flow of electricity into the device. A television is a good example, since it is partially composed of a series of individual electric components that help to conduct the flow of electricity. In like manner, desktop and laptop computers are electronic in nature. Handheld devices such as cell phones are also electronic, while operating with the use of an electric component – a battery.

_

Electrostatics is a field of science and a class of phenomena which involves charged subatomic particles, net electrical charge, electric voltage, electric fields, and attractive/repulsive electric forces. Electrodynamics is a field of science and a class of phenomena which involves electric current, magnetic fields, and attractive/repulsive magnetic forces. The study of generators, motors, circuitry, electric currents, etc., falls under the heading of “electrodynamics.”

_

History:

Electrical phenomena have been studied since antiquity, though advances in the science were not made until the seventeenth and eighteenth centuries. Long before any knowledge of electricity existed people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BC referred to these fish as the “Thunderer of the Nile”, and described them as the “protectors” of all other fish. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Thales of Miletos made a series of observations on static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. Possibly the earliest and nearest approach to the discovery of the identity of lightning, and electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning (raad) applied to the electric ray. The Parthians may have had knowledge of electroplating, based on the 1938 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature.

_

It was in 1938, while working in Khujut Rabu, just outside Baghdad in modern day Iraq that German archaeologist Wilhelm Konig unearthed a five-inch-long (13 cm) clay jar containing a copper cylinder that encased an iron rod. The vessel showed signs of corrosion, and early tests revealed that an acidic agent, such as vinegar or wine had been present.


Baghdad Batteries are dated to around 200 BC, could have been used in gilding.

_

Though most archaeologists agree the devices were batteries, there is much conjecture as to how they could have been discovered, and what they were used for. How could ancient Persian science have grasped the principles of electricity and arrived at this knowledge? Perhaps they did not. Many inventions are conceived before the underlying principles are properly understood. The Chinese invented gunpowder long before the principles of combustion were deduced, and the rediscovery of old herbal medicines is now a common occurrence. You do not always have to understand why something works – just that it does. It is certain the Baghdad batteries could conduct an electric current because many replicas have been made, including by students of ancient history under the direction of Dr Marjorie Senechal, professor of the history of science and technology, Smith College, US. Replicas can produce voltages from 0.8 to nearly two volts. Although a larger voltage can be obtained by connecting more than one battery together, it is the ampage which is the real limiting factor, and many doubt whether a high enough power could ever have been obtained, even from tens of Baghdad batteries.

_

Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined the New Latin word electricus (“of amber” or “like amber”, from the Greek word for “amber”) to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words “electric” and “electricity”, which made their first appearance in print in Thomas Browne’s Pseudodoxia Epidemica of 1646. Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge. In 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles. In 1800 A. Volta constructed and experimented with the voltaic pile, the predecessor of modern batteries. It provided the first continuous source of electricity. The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819-1820. Georg Ohm mathematically analyzed the electrical circuit in 1827. The production of induced electric currents by changing magnetic fields was demonstrated by M. Faraday in 1831. In 1851 he also proposed giving physical reality to the concept of lines of force. This was the first step in the direction of shifting the emphasis away from the charges and onto the associated fields. In 1865 J. C. Maxwell presented his mathematical theory of the electromagnetic field. This theory, which proposed a continuous electric fluid, not only synthesized a unified theory of electricity and magnetism, but also showed optics to be a branch of electromagnetism. The developments of theories about electricity subsequent to Maxwell have all been concerned with the microscopic realm. Faraday’s experiments on electrolysis in 1833 had indicated a natural unit of electric charge, thus pointing toward a discrete rather than continuous charge. While it had been the early 19th century that had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Nikola Tesla, Galileo Ferraris, Oliver Heaviside, Thomas Edison, Ottó Bláthy, Ányos Jedlik, Sir Charles Parsons, Joseph Swan, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution. The existence of electrons, negatively charged particles, was postulated by A. Lorenz in 1895 and demonstrated by J. J. Thomson in 1897. The existence of positively charged particles (protons) was shown shortly afterward (1898) by W. Wien. Since that time, many particles have been found having charges numerically equal to that of the electron. The question of the fundamental nature of these particles remains unsolved, but the concept of a single elementary charge unit is apparently still valid. Practical applications for electricity however remained few, and it would not be until the late nineteenth century that engineers were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricity’s extraordinary versatility as a means of providing energy means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrical power is the backbone of modern industrial society, and is expected to remain so for the foreseeable future.

_

Science of electricity:

_

Atom:

_


_

Everything we see is made up of tiny little parts called atoms. An atom is the smallest particle of any element that still retains the characteristics of that element. However, atoms consist of even smaller particles. Atoms consist of a central, dense nucleus that is surrounded by one or more lightweight negatively charged particles called electrons. The nucleus is made up of positively charged particles called protons and neutrons which are neutral. An atom is held together by forces of attraction between the electrons and the protons. The neutrons help to hold the protons together. The electrons actually change their orbit with each revolution.

_

Electric charge:

Like mass, length, and time, Electric Charge is a “fundamental.” Many dictionaries say this: “Electric charge: a fundamental property of matter.” The word “Charge” is used to define other things, and therefore the definition of the word “charge” becomes a serious problem! What is an electric current? It is a flow of charge. What is electric charge? It is the stuff that flows during an electric current!

_

Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Positively-charged substances are repelled from other positively-charged substances, but attracted to negatively-charged substances; negatively-charged substances are repelled from negative and attracted to positive. The electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces. Charge originates in the atom, in which its most familiar carriers are the electron and proton. It is a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire. The presence of charge gives rise to the electromagnetic force: charges exert a force on each other: like-charged objects repel and opposite-charged objects attract. The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface.

_


_


_

By convention, the charge of an electron is −1, while that of a proton is +1. Charged particles whose charges have the same sign repel one another, and particles whose charges have different signs attract. The SI unit of quantity of electric charge is the coulomb, which is equivalent to about 6.242×1018 e (e is the charge of a proton). Hence, the charge of an electron is approximately −1.602×10−19 C as the proton has a charge that is equal and opposite +1.602×10−19 coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle. The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere current within one second. That means 6.242×1018 electrons are moving in a wire every second i.e. one coulomb negative charge. The symbol Q is often used to denote a quantity of electricity or charge.

_

The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb’s law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them. Coulomb’s law quantifies the electrostatic force between two particles by asserting that the force is proportional to the product of their charges, and inversely proportional to the square of the distance between them. The influence of charges is characterized in terms of the forces between them (Coulomb’s law) and the electric field and voltage produced by them. One Coulomb of charge is the charge which would flow through a 120 watt lightbulb (120 volts AC) in one second. Two charges of one Coulomb each separated by a meter would repel each other with a force of about a million tons! The electromagnetic force is very strong, second only in strength to the strong nuclear interaction, but unlike that force it operates over all distances. In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 1042 times that of the gravitational attraction pulling them together. The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative and that by protons positive, a custom that originated with the work of Benjamin Franklin.

___


_

_


_

Electric field:

An electric field is the region around an electric charge in which an electric force is exerted on another charge. Instead of considering the electric force as a direct interaction of two electric charges at a distance from each other, one charge is considered the source of an electric field that extends outward into the surrounding space, and the force exerted on a second charge in this space is considered as a direct interaction between the electric field and the second charge.

_

The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance. However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker.

_


The figure above shows Electric Field lines emanating from a positive charge above a plane conductor.

_

The study of electric fields created by stationary charges is called electrostatics. The field may be visualized by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday, whose term ‘lines of force’ still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.

_


_

The electric field is a vector field with SI units of newtons per coulomb ((N C−1) or, equivalently, volts per meter ((V m−1). The SI base units of the electric field are kg•m•s−3•A−1.  The strength or magnitude of the field at a given point is defined as the force that would be exerted on a positive test charge of 1 coulomb placed at that point; the direction of the field is given by the direction of that force. Electric fields contain electrical energy with energy density proportional to the square of the field amplitude. The electric field is to charge as gravitational acceleration is to mass and force density is to volume.

_

So in a nutshell, electric field is produced by an electric charge even when it is not moving (i.e., there is no electric current). The electric field produces a force on other charges in its vicinity. Moving charges additionally produce a magnetic field (vide infra). So a moving charge has electric plus magnetic field known as electromagnetic field.

_

Static electricity:

Usually, atoms have the same number of electrons and protons. Then the atom has no charge, it is “neutral.” But if you rub things together, electrons can move from one atom to another. Some atoms get extra electrons. They have a negative charge. Other atoms lose electrons. They have a positive charge. When charges are separated like this, it is called static electricity. If two things have different charges, they attract, or pull towards each other. If two things have the same charge, they repel, or push away from each other. So, why does your hair stand up after you take your hat off? When you pull your hat off, it rubs against your hair. Electrons move from your hair to the hat. Now each of the hairs has the same positive charge. Things with the same charge repel each other. So the hairs try to move away from each other. The farthest they can get is to stand up and away from all the other hairs.

_

Static electricity is the accumulation of electrical charges on the surface of a material, usually an insulator or non-conductor of electricity. Static electricity is the buildup of electrical charges on the surface of some object or material. Static electricity is usually created when materials are pulled apart or rubbed together, causing positive (+) charges to collect on one material and negative (−) charges on the other surface. It is called “static” because there is no current flowing, as there is in alternating current (AC) or direct current (DC) electricity. Static electricity is usually caused when certain materials are rubbed against each other—like wool on plastic or the soles of your shoes on the carpet. It is also caused when materials are pressed against each other and pulled apart. The process causes electrons to be pulled from the surface of one material and relocated on the surface of the other material. It is called the triboelectric effect or triboelectric charging. The material that loses electrons ends up with an excess of positive (+) charges. The material that gains electrons ends up an excess of negative (−) charges on its surface. Typically, two materials are involved in static electricity, with one having an excess of electrons or negative (−) charges on its surface and the other material having an excess of positive (+) electrical charges. Atoms near the surface of a material that have lost one or more electrons will have a positive (+) electrical charge. If one of the materials is an electrical conductor that is grounded, its charges will drain off immediately, leaving the other material still charged. Static electricity can cause materials to attract or repel each other. It can also cause a spark to jump from one material to another. Comb your hair on a dry day or after using a hair drier. The plastic comb collects negative charges from the hair, causing the hair to have an excess of positive charges. Since like charges repel, the hair strand will tend to push away from each other, causing the “flyaway hair” effect. The comb with negative charges can be used to attract neutral pieces of tissue. If there are enough positive (+) electrical charges on one object or material and enough negative (−) charges on the surface of the other object the attraction between the charges may be great enough to cause electrons to jump the air gap between the objects. Once a few electrons start to move across the gap, they heat up the air, such that more and more will jump across the gap. This heats the air even more. It all happens very fast, and the air gets so hot that it glows for a short time. That is a spark (vide infra).

_

Is static electricity a misnomer?

Static and Current are two ways in which electrical charges can behave. If we said that Electrical Science is divided into two fields of research called Electrostatics and Electrodynamics, we would be correct. However, “static electricity” is a misnomer. “Static” is actually composed of forcibly ‘separated’ opposite charges, and if those separated charges should flow along, they still behave as “static electricity,” regardless of their motion. The key is the separation of the charges…while their “static-ness” is not important. For this reason, charges can behave as “static electricity” and “current electricity” both at the same time. Static Electricity appears whenever the negative charges within matter are separated from the positive charges. “Current” appears whenever the negative charges within matter are made to flow towards the positive charges (or when positive flows towards negative.) “Static” and “Current” are two separate kinds of events, they are not opposites. “Static” is a separation; it is a stretching-apart, and it really has little to do with anything remaining static or stationary. “Current” is a flowing motion. It has little to do with the separation of opposite charges.  “Static electricity” was misnamed, and it really should be called “charge separation” or maybe “stretched” or “pressurized” electricity. Since stretch is not the opposite of flow, Static is not the opposite of Current. And although electric current really exists and electric charge really exists, there is no such material as either “current electricity” or “static electricity.”

_

Imbalance of charges and not static-ness important in static electricity:

Electrostatics is about “charge,” and about the attract/repel forces which electric charge creates. The motion or the “static ness” of the charges is irrelevant. After all, the same forces continue to exist even when the charges start flowing. And charges which are separated or imbalanced can sometimes flow along, yet the “static” effects are undiminished when the current begins. In other words, it’s perfectly possible to create flows of so-called “static” electricity. It’s very misleading to concentrate on the “static ness” of the charges. It derails our explanations and hides many important concepts such as charge separation, the density of imbalanced pos/neg charge, and the presence of voltage fields surrounding the imbalanced charges. These things are important even when the “static electricity” begins moving along as a current. It’s about ‘imbalance’ between opposite charges, not about static-ness. Also, the presence of charged particles is not such an important factor, since matter is full of them, even when no “static electricity” appears. We need separated, imbalanced particle populations before interesting things start to happen. Just having charged particles is not enough. It’s the net electric charge which is important. Or put more simply: it is the separation between positive and negative particles which is the basis for “static electricity.” When quantities of protons are separated from electrons across a large distance, then we’ll get sparks and rising hair. Call this “electric charge”, not “static charge,” since the imbalance remains the same even when the charges flow along very non-statically. In fact, if the charge imbalance can be made to flow along, it will still retain all of its unusual characteristics. It will still attract hair and lint, and cause sparks, etc., even while it is flowing. This puts us into the ridiculous situation of talking about “Static Electricity” …which moves! It’s unfortunate that the term “static electricity” has become so widely adopted as the name for the phenomena. After all, charge imbalances still are “imbalances” even when they stop being static and they flow during an electric current. Also, charge-flow and charge-imbalance can happen in the same wire at the same time. Therefore, anyone who believes that “static” and “current” are two types of opposite, mutually-exclusive electricity is ignorant of the true nature of electrical phenomena.

_

“Static” or imbalanced charges can be created by removing electrons from a neutral atom. They can also be created by adding or removing charged atoms from an object, and the ions being removed can be negative or positive ions. It is even possible to add or remove bare protons from some materials (after all, protons are the same as H+ positively charged hydrogen atoms.) If you have some positively-charged water, or ice, or acid, then you probably have too many bare protons (too many H+ ions.)

_

Electrical potential:

Electric potential is the capacity of an electric field to do work on an electric charge, typically measured in volts. The concept of electric potential is closely linked to that of the electric field. In classical electromagnetism, the electric potential (a scalar quantity denoted V) at a point is equal to the electric potential energy (measured in joules) of a charged particle at that location divided by the charge (measured in coulombs) of the particle. The electric potential is independent of the test particle’s charge – it is determined by the electric field alone. The electric potential can be calculated at a point in either a static (time-invariant) electric field or in a dynamic (varying with time) electric field at a specific time, and has the units of joules per coulomb, or volts. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable. Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will ‘fall’ across the voltage caused by an electric field. The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per meter, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together.

_

Voltage is the stuff that connects the protons and electrons of atoms to each other, and it connects atoms together to form objects. Pull on your finger, and you are feeling the microscopic voltage between the atoms. Without voltage, there would be no solids or liquids in the universe, just gas. When you break a solid object, you are defeating the attractive microscopic voltages which were binding its atoms together.

_

Voltage is a major part of static electricity, so whenever we deal with voltage, we’re dealing with static electricity. If I grab electrons away from a wire, that wire will have excess protons left behind. If I place those electrons into another wire, then my two wires have oppositely-imbalanced charge. They have a voltage between them too, and a static-electric field extends across the space between them. This field ‘is’ the voltage. Electrostatic fields are measured in terms of volts per distance, and if you have an electric field, you always have a voltage. To create voltage, take charges out of one object and stick them in another. You always do this when you scuff your shoes across the carpet in the wintertime. Batteries and generators do this all the time too. It’s part of their “pumping” action.

_

Voltage, otherwise known as electrical potential difference or electric tension (denoted ∆V and measured in volts, or joules per coulomb) is the potential difference between two points — or the difference in electric potential energy per unit charge between two points. Voltage is equal to the work which would have to be done, per unit charge, against a static electric field to move the charge between two points. The voltage between two ends of a path is the total energy required to move a small electric charge along that path, divided by the magnitude of the charge. Mathematically this is expressed as the line integral of the electric field and the time rate of change of magnetic field along that path. In the general case, both a static (unchanging) electric field and a dynamic (time-varying) electromagnetic field must be included in determining the voltage between two points. A voltage may represent either a source of energy (electromotive force), or it may represent lost or stored energy (potential drop). A voltmeter can be used to measure the voltage (or potential difference) between two points in a system; usually a common reference potential such as the ground of the system is used as one of the points. Voltage can be caused by static electric fields, by electric current through a magnetic field, by time-varying magnetic fields, or a combination of all three. Voltage is defined so that negatively-charged objects are pulled towards higher voltages, while positively-charged objects are pulled towards lower voltages. Therefore, the conventional current in a wire or resistor always flows from higher voltage to lower voltage. Current can flow from lower voltage to higher voltage, but only when a source of energy is present to “push” it against the opposing electric field. For example, inside a battery, chemical reactions inside the battery provide the energy needed for current to flow from the negative to the positive terminal. A common voltage for flashlight batteries is 1.5 volts (DC). A common voltage for automobile batteries is 12 volts (DC). Common voltages supplied by power companies to consumers are 110 to 120 volts (AC) and 220 to 240 volts (AC). The voltage in electric power transmission lines used to distribute electricity from power stations can be several hundred times greater than consumer voltages, typically 110 kV to 1,200 kV (AC) . The voltage used in overhead lines to power railway locomotives is between 12 kV and 50 kV (AC).

_

If the electrical force moves a charge a certain distance, it does work on that charge. The change in electric potential over this distance is defined through the work done by this force: where potential is shorthand for change in electric potential, or potential difference. This is analogous to the definition of the gravitational potential energy through the work done by the force of gravity in moving a mass through a certain distance. The units of potential difference, or simply potential, are Joules / Coulomb, which are called Volts (V). Physically, potential difference has to do with how much work the electric field does in moving a charge from one place to another. Batteries, for example, are rated by the potential difference across their terminals. In a nine volt battery the potential difference between the positive and negative terminals is precisely nine volts. On the other hand the potential difference across the power outlet in the wall of your home is 110 volts in America and 220 volts in India.

_

Voltage is “Potential”, and potential is not pressure, even though a potential-difference can “push” upon the electrical charges.  Here’s one way to imagine it. Suppose we roll a boulder up a hill. This stores potential energy and we get the energy back if the boulder rolls back down. Electrostatic fields are like gravity, and voltage is like the height of the hill. The higher we go, the more “gravitational potential” we put into the boulder. But height is not pressure, and the hill is still there even when the boulder is gone. In a similar way, we need both voltage and charges before there can be any “electrical pressure.” The voltage only causes a “push” when the charges are present. Voltage can appear in space, but if there are no charges, then no pushing-force or “pressure” exists. To make a conductor’s charges start moving, just apply some voltage across that conductor. Since copper wire is a good conductor having free electrons, voltage will cause charges to move. However, if the same voltage is applied to insulator, no charge will move as insulator has no free electrons. So voltage can generate current only if charges are available to flow, causing electricity to flow and also electrical energy to flow.

_

Voltage is the difference in electrical potential energy. So a 12-volt battery comes with a bigger built-in “height” than a 9-volt battery.  A volt can be defined as “the amount of change in potential that will cause a one-ampere current to give one watt of power. Another way of saying this is: Power is voltage times current. So as the current gets bigger, so does the power, and when the voltage gets higher the power also increases.

_

Whenever a negative charge attracts a positive charge, invisible fields of voltage must exist between the charges. Voltage causes the attraction between opposite charges; the voltage fields reach across space. In reality, “static” electricity has nothing to do with motion (or with being static.) Instead static electricity involves high voltage. Scuff across a rug, and you charge your body to several thousand volts. When you remove a wool sock from your clothes dryer, and all the fibers stand outwards, the fibers are following the invisible lines of voltage in the air. Fibers are the “iron filings” that make the voltage patterns visible. And whenever the charges within a conductor are forced to flow, they only move because they’re being driven along by a voltage-field which runs through the length of the wire. Voltage causes current. Voltage causes dryer-cling, but it also causes electric currents in wires. Another way to say it: electric currents are caused by “static electricity,” and “static electricity” is not necessarily static. To be a bit more specific, Voltage is a way of using numbers to describe an electric field. Electric fields or “E-fields” are measured in volts over a distance; volts per centimeter for example. A stronger e-field has more volts per centimeter than a weaker one. Volts are always measured along the flux lines of electric field, therefore voltage is always measured between two charged objects. If I start at the negative end of my flashlight battery, I can call that end “zero volts”, and so the other end must be positive 1.5 volts. However, if I start at the positive end instead, then the positive battery terminal is zero volts, and the other terminal is negative 1.5 volts. Or, if I start half way between the battery terminals, then one terminal is -0.75 volts, and the other terminal is +0.75 volts.

__

There are three common ways to create voltages which can push electric charges along:

  1. Move a magnet past a conductor.
  2. Place two different conductors into some salt water.
  3. Touch two different conductors together, then shine some light on them.

It’s also a list of the three common kinds of electrical power supply:

  1. ELECTRIC COMPANY GENERATOR: Move a magnet past a conductor.
  2. BATTERY: Place two different conductors into some salt water.
  3. SOLAR CELL: Touch two different conductors together, then shine light on them.

__

What about shocks when I get out of my car?

Many people experience shocks when they get out of their car. Often they believe that the car is charged – but this is not normally so. Sitting in the car, electrostatic charges are generated on the car seat and the person’s body, due to contact and movement between the clothes and the seat. When the person leaves the seat, they take half of this charge with them. As they get out of the vehicle, their body voltages rises due to this charge – a voltage of 10,000 Volts is not unusual. But it only lasts for ten billionths of a second, and the total energy that flows into the spark is very low. When they reach to touch the vehicle door, the electrostatic discharge and shock occurs as their hand approaches the metal door. The voltage build-up can often be avoided by holding onto a metal part of the door frame as you leave the seat. This provides a return dissipation path for the charge on your body. If you have forgotten to hold the metal door part as you leave the seat, a shock may often still be avoided by touching the glass window before you touch the metal door. The glass may be conductive enough to dissipate charge, whilst preventing the rapid discharge which is felt as a shock.  If you have your keys in your hand – let the spark discharge through the keys not to your fingers, and you won’t feel anything!

__

Electric current:

Electric current is a movement or flow of electrically charged particles, typically measured in amperes. The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current. By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively charged electrons around an electric circuit, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. An electric current appears whenever the negative charges in an object are forced to flow through the positive charges, or when positive charges are forced to flow through negative ones. Or when the positives and negatives are forced to flow in opposite directions at the same time.

_

A current of 1 ampere means that there is 1 coulomb of charge passing through a cross section of a wire every 1 second.

1 ampere = 1 coulomb / 1 second

The direction of an electric current is by convention the direction in which a positive charge would move. Thus, the current in the external circuit is directed away from the positive terminal and toward the negative terminal of the battery. Electrons would actually move through the wires in the opposite direction. Knowing that the actual charge carriers in wires are negatively charged electrons may make this convention seem a bit odd and outdated. Nonetheless, it is the convention that is used worldwide and one that a student of physics can easily become accustomed to.

_


__

Ohm’s law:

_


_

Ohm’s law simply says that the rate of charge flow is directly proportional to the voltage difference, and if the voltage goes up, the flow goes up in proportion. It also says that the resistance affects the charge flow. If the resistance goes up while the voltage-difference stays the same, the flow gets less by an “inverse” proportional amount. The harder you push, the faster it flows. The bigger the resistance, the smaller the flow (if the push is kept the same.) That’s Ohm’s law.

_

In a normal conductor, an electric current may be visualized as a fluid of electrons moving across a heavy ionic lattice. The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat, which is essentially the vibrational kinetic energy of the lattice ions. As a result, the energy carried by the current is constantly being dissipated. This is the phenomenon of electrical resistance.

_

The volt is the difference in EMF (electromotive force: the push behind the electrons) which will give a coulomb of electrons a joule of energy. The ohm is the unit of resistance to flow of electrons (perfect conductors do not exist except at very low temperatures) which will require a volt of EMF to drive one ampere of current. The watt is the amount of power required to keep pushing a coulomb of charge each second (an ampere) with (against) an EMF of one volt. A one volt source connected to a one ohm resistance will cause one ampere of current to flow and produce one joule of heat energy each second.

_

Is electricity means flow of electrons?

Charges of “electricity” are carried both by electrons and protons. These two types of particles have very different weights (mass), but both have exactly the same amount of electric charge. Electrons are easily removed from atoms, while protons usually are stuck to other protons, but that doesn’t affect the amount of charge they carry. If we remove an electron from an atom, that atom is left with too many protons, and that’s the only reason why the atom has an excess of positive electric charge. Electric currents are not just flows of electrons; they are flows of any type of electric charge. Both protons and electrons possess exactly the same amount of ‘electricity.’ If either the protons or the electrons flow, that flow is an electric current. In the everyday world of electronics, these particles are the electrons and protons supplied by atoms in conductors. Physicists may additionally deal with other charged particles: muons, positrons, antiprotons, etc. But the “electricity” in common electrical devices is limited to positive protons and negative electrons. Because the negative particles carry a name that sounds like “electricity,” people unfortunately start thinking that the electrons are the electricity, and they think that that protons (having a much less electrical name?) are not electrical. Now everyone will rightly tell me that the protons within wires cannot flow, while the electrons can. Yes, this is true… but only true for metals. And it’s only true for solid metals. All metals are composed of positively charged atoms immersed in a sea of movable electrons. When an electric current is created within a solid copper wire, the “electron sea” moves forward, but the protons within the positive atoms of copper do not. However, solid metals are not the only conductors, and in many other substances the positive atoms ‘do’ move, and they ‘do’ participate in the electric current. These various conductors are nothing exotic. They are very common, they all around us; as close to us as they can possibly be. Electric currents in a metal wire are flows of electrons, but in many other materials both the positive and negative charges can flow. For example, when you get an electric shock, no electrons flow through your body. During electrocution, it is these charged atoms which flowed along as an electric current. The electric current was a flow of positive sodium and potassium atoms, negative chlorine, and numerous other more complex positive and negative molecules. During the electric current, the positive atoms flows in one direction, while the negative atoms simultaneously flows in the other direction in your tissues during electric shock. The same is true of electrical currents in salt water, in the ground, and in battery electrolyte. When your car battery is supplying 300 amps to the starter motor, 300A worth of ions is flowing through the battery acid, and approximately half of these are carrying positive charge. Also, plasmas can have positive ion currents as well as negative electron flows: examples are neon signs, fluorescent lights, camera flashes, and sparks of all kinds. There are even some conductors where the current is a flow of positive hydrogen ions, +H ions, otherwise known as protons. One common “proton conductor” is ice. Other proton-conductors are used as solid electrolytes in exotic batteries and, more recently, are found as proton-conductor solid electrolyte membranes in tiny fuel cells. In salt water, in fluorescent bulbs, and in battery acid, atoms with extra protons can flow along, and this flow is a genuine electric current. And in fuel cell membranes and in solid ice, electric current is actually a flow of single protons.

__

Two way current:

Two-way currents are common: When you connect a lightbulb to a battery, you form a complete circuit, and the path of the flowing charge is through the inside of the battery, as well as through the light bulb filament. Battery electrolyte is very conductive. Down inside the battery, within the wet chemicals between the plates, the amperes of flashlight current appears as a flow of both positive and negative atoms. There is a powerful flow of electric charge going through the battery, yet no individual electrons flow through the battery at all. So, while the current is between the two plates of the battery, what’s its real direction? Not right to left, not left to right, but in both directions at once. About half of the charge-flow is composed of positive atoms, and the remaining portion is composed of negative atoms flowing backwards. Of course in metal wires outside the battery, the real particle flow is only from negative to positive. But inside the battery’s wet electrolyte, the charge-flow goes in two opposite directions at the same time.

_

There are many other places where this kind of positive/negative charge flow can be found. In the following list of devices and materials, electric charges found within conductors are a combination of movable positive and negative particles. During an electric current, both varieties of particles are flowing past each other in opposite directions.

TWO-WAY Pos/Neg electric current can exist in:

  • batteries
  • human bodies
  • all living organisms
  • the ground
  • the ocean
  • the sky (ionosphere)
  • electrolytic capacitors
  • aluminum smelters
  • liquid mercury and solder
  • ion-based smoke detectors
  • electroplating tanks
  • electrophoresis gels in research (esp. DNA testing)
  • air cleaners, smoke precipitators
  • particle beams
  • the vertical “sky current” in the atmosphere
  • gas discharge, which includes: electric sparks, fluorescent tubes, sodium and mercury arc streetlights, neon signs, the Earth’s Aurora, lightning and corona discharges, arc welders, Geiger counter tubes, thyratron tubes and mercury vapor rectifiers.

_


_

Effects of electric current:

Electric currents produce three main effects: magnetism, heating, and the voltage drop across resistive conductors. These three effects cover almost everything we encounter in electronics. And these three effects don’t care about the amounts of positive and negative particles, or about their speed, their mass, their charge, etc. If a hundred positive particles flow to the left per second, this gives exactly as much magnetism, heating, and voltage as a hundred negative particles flowing to the right per second. (Note: this is because reversing the polarity of the particles reverses the current, and reversing the particle direction reverses the current again! Two negatives make a positive.) Magnetism, heating, and voltage drop together represent nearly every feature that’s important in everyday electrical circuitry. Therefore, as far as most electrical devices and circuits are concerned, it makes no difference if the current is made of positive particles going one way, or negative particles going the other… or half as many negatives flowing backwards through a crowd of half as many positives.

_

By convention, we define the flowing charges to be positive. Or to put it simply: we pretend that “electric currents” are always composed of  positive particles, so that any negative currents are defined as positive particles flowing backwards rather than negative particles flowing forwards.

_

Current versus drift speed:

Current has to do with the number of coulombs of charge that pass a point in the circuit per unit of time. Because of its definition, it is often confused with the quantity drift speed. Drift speed refers to the average distance traveled by a charge carrier per unit of time. Like the speed of any object, the drift speed of an electron moving through a wire is the distance to time ratio. The path of a typical electron through a wire could be described as a rather chaotic, zigzag path characterized by collisions with fixed atoms. Each collision results in a change in direction of the electron. Yet because of collisions with atoms in the solid network of the metal conductor, there are two steps backwards for every three steps forward. With an electric potential established across the two ends of the circuit, the electron continues to migrate forward. Progress is always made towards the positive terminal. Yet the overall affect of the countless collisions and the high between-collision speeds is that the overall drift speed of an electron in a circuit is abnormally low. A typical drift speed might be 1 meter per hour. That is slow! Current is the rate at which charge crosses a point on a circuit. A high current is the result of several coulombs of charge crossing over a cross section of a wire on a circuit. If the charge carriers are densely packed into the wire, then there does not have to be a high speed to have a high current. That is, the charge carriers do not have to travel a long distance in a second, there just has to be a lot of them passing through the cross section. Current does not have to do with how far charges move in a second but rather with how many charges pass through a cross section of wire on a circuit. To illustrate how densely packed the charge carriers are, we will consider a typical wire found in household lighting circuits – a 14-gauge copper wire. In a 0.01 cm-long (very thin) cross-sectional slice of this wire, there would be as many as 3.51 x 1020 copper atoms. Each copper atom has 29 electrons; it would be unlikely that even the 11 valence electrons would be in motion as charge carriers at once. If we assume that each copper atom contributes just a single electron, then there would be as much as 56 coulombs of charge within a thin 0.01-cm length of the wire. With that much mobile charge within such a small space, a small drift speed could lead to a very large current.

_

Electric currents in copper wires are a flow of electrons, but these electrons are not supplied by batteries. Generators do not ‘generate’ any electrons. Instead the electrons come from the wire. In copper wire, copper atoms supply the flowing electrons. Batteries and generators cause electric charge to flow. Essentially the metal’s electrons are “jumping” from atom to atom all the time, even when there is no electric current applied. Physicists call this the “electron sea” or “electron gas” of the metal. The “electron sea” of metals gives them their characteristics: most other materials will shatter, but metals stay bent because the electrons fill in the gaps. Also, the electron sea is visible to human eyes: it has a silvery color because movable electrons reflect light. When there is an electric current in a wire, it is these movable electrons which flow. These electrons are not stuck to individual metal atoms in the first place, so they do not need to “jump” during an electric current. The orbiting motion of the metal’s “liquid” electrons takes place at high speed. Doesn’t this mean that charge moves fast in wire? No, because this motion has no average direction and is similar to the random thermal vibrations of a gas. It’s like a vibration, and it’s happening all the time, even when the “wind speed” inside the wire is zero. For this reason we normally ignore the wandering motion of individual electrons, just as we ignore the fast vibration of water molecules when we talk about the speed of a river. And air molecules keep moving fast even when there is no wind at all. The velocity of charges flowing during electric currents is the average “drift velocity,” and when the current falls to zero and the charges aren’t flowing, they’re still wiggling randomly around at very high velocity. A battery does not supply charges, it merely pumps them. Whenever electric charge flows into one terminal of a battery, an equal amount of charge must flow through the battery and back out through the other terminal. In a simple battery/bulb circuit, the charges are forever flowing around and around the circuit, going through both the battery and the bulb. The battery is a charge pump.

_

It is also a fact that the electrons flowing in ordinary copper wires carrying normal direct currents move at about the speed of a snail, and when carrying 60Hz alternating current oscillate within only about 1/500mm or 2 microns of distance.

_


_

When electric current in a material is proportional to the voltage across it, the material is said to be “ohmic”, or to obey Ohm’s law. A microscopic view suggests that this proportionality comes from the fact that an applied electric field superimposes a small drift velocity on the free electrons in a metal. For ordinary currents, this drift velocity is on the order of fraction of millimeter per second in contrast to the speeds of the electrons themselves which are on the order of a million meters per second. The Bohr model of the hydrogen atom has the (bound) electron zipping around the nucleus at about 2 million meters/sec. Even the electron speeds are themselves small compared to the speed of transmission of an electrical energy down a wire, which is on the order of the speed of light, 300 million meters per second in an un-insulated copper wire.

_

Speed of electricity-drift velocity of electrons v/s speed of EM energy:

The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave, not the movement of electrons. Electromagnetic wave propagation is fast and depends on the dielectric constant of the material. In a vacuum the wave travels at the speed of light and almost that fast in air. Propagation speed is affected by insulation, such that in an unshielded copper conductor range 95 to 97% that of the speed of light, while in a typical coaxial cable it is about 66% of the speed of light at about 120,000 mph. At 60 cycles per second, the wavelength is 5000 kilometers, and even at a hundred thousand Hertz, the wavelength is 3 kilometers. That is very great compared to the distance to which electric fields usually extend. The drift velocity deals with the average velocity that a particle, such as an electron, attains due to an electric field. In general, an electron will ‘rattle around’ in a conductor at the Fermi velocity randomly. Free electrons in a conductor vibrate randomly, but without the presence of an electric field there is no net velocity. When a DC voltage is applied the electrons will increase in speed proportional to the strength of the electric field. These speeds are on the order of one meter per hour. AC voltages cause no net movement; the electrons oscillate back and forth in response to the alternating electric field.

_

So in a nutshell approximately:

Fermi speed of electron = 2 million meter per second around the nucleus of atom

Drift velocity of electron = one meter per hour or 0.3 mm per second in DC circuit

Drift velocity of electron = oscillates distance of 2 microns in AC circuit 50 to 60 times a second depending of frequency

Electrical energy/signal speed = near to speed of light in un-insulated copper wire

Electrical energy/signal speed = 66 % of speed of light in coaxial copper cable

_

Electric conduction:

Since a current is a flow of charge, the common expression “flow of current” should be avoided, since literally it means “flow of flow of charge.” The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids. While the particles themselves can move quite slowly, sometimes with average drift velocity only fractions of a millimeter per second, the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires.

_

Matter, as you probably know, is composed of atoms. Break something down to small enough pieces and you wind up with a nucleus orbited by one or more electrons, each with a negative charge. In many materials, the electrons are tightly bound to the atoms. Wood, glass, plastic, ceramic, air, cotton — these are all examples of materials in which electrons stick with their atoms. Because these atoms are so reluctant to share electrons, these materials can’t conduct electricity very well, if at all. These materials are electrical insulators. Most metals, however, have electrons that can detach from their atoms and zip around. These are called free electrons. The loose electrons make it easy for electricity to flow through these materials, so they’re known as electrical conductors. They conduct electricity. The moving electrons transmit electrical energy from one point to another.

_

Conductors and insulators:

A conductor is a material which allows an electric current to pass. Metals are good conductors of electricity. An insulator is a material which does not allow an electric current to pass. Nonmetals are good insulators of electricity. Plastic, glass, wood, and rubber are good insulators. In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons. Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell. Insulators are non-conducting materials with few mobile charges and which support only insignificant electric currents. All conductors contain electrical charges, which will move when an electric potential difference (measured in volts) is applied across separate points on the material. This flow of charge (measured in amperes) is what is meant by electric current. In most materials, the direct current is proportional to the voltage (as determined by Ohm’s law), provided the temperature remains constant and the material remains in the same shape and state. Most familiar conductors are metallic. Copper is the most common material used for electrical wiring. Silver is the best conductor, but it is expensive. Because gold does not corrode, it is used for high-quality surface-to-surface contacts. However, there are also many non-metallic conductors, including graphite, solutions of salts, and all plasmas. There are even conductive polymers.

_

If we place a Potential Difference across either air or a vacuum, no electric current appears. Air and vacuum are insulators. This is sensible, since there are few movable charges in air or vacuum, so a voltage placed across them is unable to cause an electric current. If we place a voltage across a piece of metal or across a puddle of salt water, the charges present in those materials will flow, and an electric current will appear, since these substances are always full of movable charges, and therefore the “voltage pressure” causes the charges to flow. In metal, the outer electrons of the atoms are not bound upon individual atoms but instead can move through the material, and a voltage can drive these “liquid” electrons along. But if we stick our wires into oil, there will be no electric current, since oil does not contain movable charges. If we were to inject charges into a vacuum, then we would have electric current in a vacuum. This is how TV picture tubes and vacuum tubes work; electrons are forcibly injected into the empty space by a hot filament. However, think about it for a second: it’s no longer a vacuum when it contains a cloud of electrons! Maybe we should change their name to “electron-cloud tubes” rather than “vacuum tubes”, since the electron cloud is required before there can be any conductivity in the vacuum between the plates.

_

An electrical insulator is a material whose internal electric charges do not flow freely, and which therefore does not conduct an electric current, under the influence of an electric field. A perfect insulator does not exist, but some materials such as glass, paper and Teflon, which have high resistivity, are very good electrical insulators. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to insulate electrical wiring and cables. Examples include rubber-like polymers and most plastics. Such materials can serve as practical and safe insulators for low to moderate voltages (hundreds, or even thousands, of volts).

_


_

The figure above shows that whether a material is an insulator depends on its band gap, the energy needed by an electron to make it a conduction electron so it can move freely. Materials with a wide band gap have very few conduction electrons, making them insulators.

_

Does water and oil conduct electricity?

Pure distilled water is a very poor conductor of electricity. However, most of tap water has little amount of salt dissolved in it. Dissolving salt in water produces ions (charged chemical species) which act as charge carriers. As a result, tap water is a much better electrical conductor than is pure water. A good lubricant is not necessarily non-conductive. Soapy water is a good lubricant and is also a fair conductor of electricity. Engine oil does not conduct electricity because there are no charge carriers in it. A charge carrier is any chemical species with a net electric charge. In the case of motor oils, there are no charge carriers. Furthermore, salts are not soluble in oil so it isn’t usually possible to add a charge carrier to increase the electrical conductivity. In metals, the “charge carriers” are electrons. A hunk of metal is essentially a single molecule. Some of the metals electrons are not held tightly to an individual atom and can migrate through the metal under the influence of an electric field. In oil there are no loosely held electrons in the individual molecules, hence no possibility for the electrons to migrate within a molecule. Even if there were loosely held electrons within the molecules, there is no low energy mechanism to transfer mobile electrons between molecules. So, oil is non-conductive because it doesn’t contain any charge carriers. Oil usually cannot be made conductive by the addition of salts.

_

Magnetism:

_


_

The electron is a charged particle of charge (−e), where e is the elementary charge. Its angular momentum comes from two types of rotation: spin and orbital motion. From classical electrodynamics, a rotating electrically charged body creates a magnetic dipole with magnetic poles of equal magnitude but opposite polarity. This analogy holds as an electron indeed behaves like a tiny bar magnet. One consequence is that an external magnetic field exerts a torque on the electron magnetic moment depending on its orientation with respect to the field. A spinning charged particle such as hydrogen nucleus generates a magnetic field. The direction of the magnetic field generated by the spinning charged particle depends on the rotational direction of the particle.

_

All moving charged particles produce magnetic fields. Moving point charges, such as electrons, produce complicated but well known magnetic fields that depend on the charge, velocity, and acceleration of the particles. Magnetic fields are produced by moving electric charges and the intrinsic magnetic moments of elementary particles associated with a fundamental quantum property, their spin. Permanent magnets are objects that produce their own persistent magnetic fields. They are made of ferromagnetic materials, such as iron and nickel, that have been magnetized, and they have both a north and a south pole.

_

Magnetism is a force of attraction or repulsion that acts at a distance. It is due to a magnetic field, which is caused by moving electrically charged particles or is inherent in magnetic objects such as a magnet. A magnet is an object that exhibits a strong magnetic field and will attract materials like iron to it. Magnets have two poles, called the north (N) and south (S) poles. Two magnets will be attracted by their opposite poles, and each will repel the like pole of the other magnet.

_

Attraction:

When two magnets or magnetic objects are close to each other, there is a force that attracts the poles together.


Magnetic Force attracts N to S

Magnets also strongly attract ferromagnetic materials such as iron, nickel and cobalt.

_

Repulsion:

When two magnetic objects have like poles facing each other, the magnetic force pushes them apart.


Magnets can also weakly repel diamagnetic materials.

_

The magnetic and electric fields are both similar and different. They are also inter-related. Electric charges and magnetism are similar in the sense that just as the positive (+) and negative (−) electrical charges attract each other, the N and S poles of a magnet attract each other. In electricity like charges repel, and in magnetism like poles repel. Electric charges and magnetism are different in the sense that the magnetic field is a dipole field. That means that every magnet must have two poles. On the other hand, a positive (+) or negative (−) electrical charge can stand alone. Electrical charges are called monopoles, since they can exist without the opposite charge.

_

Magnetism is a property of materials that respond to an applied magnetic field. Permanent magnets have persistent magnetic fields caused by ferromagnetism. That is the strongest and most familiar type of magnetism. However, all materials are influenced varyingly by the presence of a magnetic field. Some are attracted to a magnetic field (paramagnetism); others are repulsed by a magnetic field (diamagnetism); others have a much more complex relationship with an applied magnetic field (spin glass behavior and antiferromagnetism). Substances that are negligibly affected by magnetic fields are known as non-magnetic substances. They include copper, aluminum, gases, and plastic. Pure oxygen exhibits magnetic properties when cooled to a liquid state.

_

Ferromagnetism occurs (permanent magnet) because dipole magnetic charges of all individual atoms are aligned together strengthening magnetic field producing a north and south pole of a magnet. In non-magnetic substance, individual dipole magnetic charges of atoms are randomly placed neutralizing magnetic fields of each other.

_

Earth as magnet:

The Earth’s core is iron, and we know it has a North Pole and a South Pole. These aren’t just geographical designations but actual opposing magnetic poles. The dynamo effect, a phenomenon that creates massive electrical currents in the iron thanks to the movement of liquid iron across the outer core, creates an electrical current. This current generates a magnetic charge, and this natural magnetism of the Earth is what makes a compass work. A compass always points north because the metal needle is attracted to the pull of the North Pole.

_

A magnetic field consists of imaginary lines of flux coming from moving or spinning electrically charged particles. Examples include the spin of a proton and the motion of electrons through a wire in an electric circuit. The lines of magnetic flux flow from one end of the object to the other. By convention, we call one end of a magnetic object the N or North-seeking pole and the other the S or South-seeking pole, as related to the Earth’s North and South magnetic poles. The magnetic flux is defined as moving from N to S. Although individual particles such as electrons can have magnetic fields, larger objects such as a piece of iron can also have a magnetic field, as a sum of the fields of its particles. If a larger object exhibits a sufficiently great magnetic field, it is called a magnet. The magnetic field of an object can create a magnetic force on other objects with magnetic fields. That force is what we call magnetism. When a magnetic field is applied to a moving electric charge, such as a moving proton or the electrical current in a wire, the force on the charge is called a Lorentz force.

_


_

Sources of magnetism:

Magnetism, at its root, arises from two sources:

1. Electric currents or more generally, moving electric charges create magnetic fields.

2. Many particles have nonzero “intrinsic” (or “spin”) magnetic moments. Just as each particle, by its nature, has a certain mass and charge, each has a certain magnetic moment.

In magnetic materials, sources of magnetization are the electrons’ orbital angular motion around the nucleus, and the electrons’ intrinsic magnetic moment (electron magnetic dipole moment). The other sources of magnetism are the nuclear magnetic moments of the nuclei in the material which are typically thousands of times smaller than the electrons’ magnetic moments, so they are negligible in the context of the magnetization of materials. Nuclear magnetic moments are important in other contexts, particularly in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). Ordinarily, the enormous number of electrons in a material is arranged such that their magnetic moments (both orbital and intrinsic) cancel out.  However, sometimes — either spontaneously, or owing to an applied external magnetic field — each of the electron magnetic moments will be, on average, lined up. Then the material can produce a net total magnetic field, which can potentially be quite strong. The magnetic behavior of a material depends on its structure, particularly its electron configuration, for the reasons mentioned above, and also on the temperature. At high temperatures, random thermal motion makes it more difficult for the electrons to maintain alignment.

_

The most common source of a magnetic field is an electric current loop. The motion of electric charges in a pattern produces a magnetic field and its associated magnetic force. Similarly, spinning objects, like the Earth, produce magnetic fields, sufficient to deflect compass needles. Today we know that permanent magnets are due to dipole charges inside the magnet at the atomic level. A dipole charge occurs from the spin of the electron around the nucleus of the atom. Materials (such as metals) which have incomplete electron shells will have a net magnetic moment. If the material has a highly ordered crystalline pattern (such as iron or nickel), then the local magnetic fields of the atoms become coupled and the material displays a large scale bar magnet behavior.

_


_

Magnetism vis-à-vis electricity:

The relationship between electricity and magnetism is intimate. A changing magnetic field induces electrical current in a wire, and is the basis for electrical generation. Also, an electrical current flowing through a wire creates a magnetic field, and is the basis for most motors. In general, a changing magnetic field creates an electrical field, and a changing electrical field creates a magnetic field. In fact, light is exactly this; two fields oscillating at right angles, and inducing one another through space. One of the four fundamental forces in the universe is the electromagnetic force. Not the electric or the magnetic force, but the electromagnetic force. Basically, you can’t have electricity without magnetism and vice versa. That may not make electricity and magnetism exactly the same, but they are intertwined in a most intimate way.

_

An electric current flowing in a wire creates a magnetic field around the wire as seen in the figure below.


The amount of magnetic field force generated by a coiled wire is proportional to the current through the wire multiplied by the number of “turns” or “wraps” of wire in the coil. This field force is called magnetomotive force (MMF), and is very much analogous to electromotive force (EMF) in an electric circuit.

__

Electromagnetism:

Maxwell’s equations say that electricity and magnetism are related:

1. Changing electric fields produce magnetic fields

2. Changing magnetic fields produce electric fields

3. Changing electric and magnetic fields travel out form their source as a wave in a straight line at the velocity of light

4. Constant electric fields do not produce magnetic fields

5. Constant magnetic fields do not produce electric fields

6. Magnetic monopoles cannot exist, i.e. there cannot be a magnet with only a north or only a south pole

_

Maxwell’s equations also tell us about the geometric relations between electric and magnetic fields specifically in regard to circuits:

1. A straight current carrying wire produces a magnetic field that wraps around the wire in a circular manner according to the right hand rule.

2. A current carrying circular wire loop produces a magnetic field similar to that of a bar magnet with a north and a south pole

3. A changing linear magnetic field will produce a circular electric field

_

Faraday’s Law:

Any change in the magnetic environment of a coil of wire will cause a voltage (EMF) to be “induced” in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.

_

Lenz’s Law:

When an EMF is generated by a change in magnetic flux according to Faraday’s Law, the polarity of the induced EMF is such that it produces a current whose magnetic field opposes the change which produces it. The induced magnetic field inside any loop of wire always acts to keep the magnetic flux in the loop constant.

_

Electromagnetism (EM) vis-à-vis voltage and current:

In the word “Electromagnetism,” the term “electro” does not refer to electricity. Instead it refers… to voltage! Electromagnetism is the study of electric fields and magnetic fields: electro/magnetism. The charge flow (electric current) is intimately associated with magnetism, while the separated opposite charges are intimately associated with voltage. So voltage means imbalanced separated opposite charges creating electrical field and potential. Current means flow of charges creating magnetic field. Voltage is associated with electrostatic fields in space. Whenever you have a voltage, you also have an electric field.  Current is associated with magnetic fields in space. Whenever you have an electric current, you also have a magnetic field. Electrical energy has two faces: magnetism and “electricism” (magnetic fields and electrostatic fields.) Where do voltage and current come in? Easy: the voltage is part of electric fields, and the current is part of magnetic fields. For example, whenever the charges in a coil of wire are forced to flow along, a magnetic field appears around the coil, and energy is stored in the magnetic field. Even if the wire is straight and is not wound into a coil, there is still a magnetic field surrounding the electric current in the wire. We could almost say that electric current is the energy, since whenever a current exists, there must be a magnetic field and there must be energy present in that field. (We could almost say that, but not quite, since all the energy is sitting in the fields and it’s not moving along with the flowing charges inside the wires.). In a similar way, voltage is profoundly connected with electric fields. Whenever we “charge” up a capacitor, energy is stored in the electrostatic field between the capacitor plates. The wires of an electric circuit can also act like capacitor plates, and energy will be stored in the voltage-fields that surround the circuit. If we have voltage, then we must have an e-field, so we must have some electrical energy present. When voltage and current exist together in a medium, electrical field gets interwined with magnetic field producing electrical energy as electromagnetic waves flowing around the conductor at speed of light. A flow of electromagnetic energy along a cable is composed half of electric current, and half of voltage. It is “voltagecurrent,”  – it’s electro-magnetism. Electromagnetism is a two-sided coin, so what is voltage? Its one side of EM (the other side being magnetism.). Electrical kinetic energy (KE) appears whenever positive charges flow through negative charges or negative charges flowing through positive charges. We call this “electric current,” and it causes magnetism. On the other hand, electrical potential energy (PE) appears whenever positive charges are yanked away to a distance from their corresponding negative charges. We call this “net electrostatic charge,” and it causes voltage. Electrical KE is associated with current, and electrical PE is associated with voltage. If electrical energy is the same as Electromagnetism, then maybe we should be more sensible and name it “VoltageCurrent-ism.”  Voltage and current are two independent things. It is easy to create a current which lacks a voltage: just short out an electromagnet coil. Also, a ring of ‘Superconductor’ can contain a loop of flowing charge that flows inside it forever. It’s like frictionless motion (with no force needed to keep it going.) It’s like a flywheel which keeps spinning forever. It is also easy to create a voltage without a current: flashlight batteries maintain their voltage even when they are sitting on the shelf in the store. Water analogy: Think of water pressure without a flow. That’s like voltage alone. Now think of water that’s coasting along; a water flow without a pressure. That’s like electric current alone. Voltage is like an electrical pressure or push; it can cause electric charges to flow. So voltage can cause current if it can overcome resistance in a conductor. Or, if flowing charge is suddenly blocked, this can cause a voltage to appear. But current can exist without voltage, and voltage can exist without current. Potential energy involves stretching, squeezing, pressure and forces. Voltage is associated with electric charge which has been “stretched” or “pressurized.”  Spin a flywheel, that’s an analogy for electric current and magnetism. Stretch a rubber band, that’s an analogy for voltage and charge separation. Voltage and magnetism can be combined to become a traveling wave of warped space. We call these waves “light,” or “radio waves,” or “electrical energy.” When the Electric Utility Companies sell you some “electricity”, they really are selling you pulses of “space warp” which are guided to you by a pair of copper wires. They are selling you a combination of voltage and current. When voltage and current are there, electromagnetic energy is flowing down the wires.

__

It’s true that electromagnetism has a wide variety of behaviors. Its behavior depends on the strengths of the electric field and magnetic field involved. Electric field corresponds to voltage, and magnetic field corresponds to current. The “map” below is intended to show us that “static electricity” and “current electricity” are really just two fields of science. But electromagnetism itself is a seamless whole, and the boundaries between its various parts exist only in our minds.

_


_

In EM, its electric field corresponds to voltage, and its magnetic field corresponds to current. Therefore it’s possible to place “static electricity” and “current electricity” upon different regions of a single map. The map above is plotted in terms of e-field (voltage) on one axis and magnetism (current) on the other. Does this tell us that there really is no such thing as “static electricity” or “current electricity”?  Yes! Only electrical devices and electrical phenomena exist, and these devices and phenomena can have various ratings of voltage and current. In view of the “electricity map”, here is how we usually divide up Electricity:

Static Electricity = Electrical happenings which involve HIGH VOLTAGE at low current.

Current Electricity = Electrical happenings which involve HIGH CURRENT at low voltage.

_

Conductive path of a current in a circuit:


All conductive materials contain movable charges. The resistor and the battery’s electrolyte both are conductive. When we include them with the wires, we can see that an electric circuit is a complete circle which is full of “fluid” charge. It acts like a liquid flywheel; a flywheel hidden inside a closed ring of pipe.

_

Whether you are using a battery, a fuel cell or a solar cell to produce electricity, three things are always the same:

1. The source of electricity must have two terminals: a positive terminal and a negative terminal.

2. The source of electricity (whether it is a generator, battery or something else) will want to push electrons out of its negative terminal at a certain voltage. For example, one AA battery typically wants to push electrons out at 1.5 volts.

3. The electrons will need to flow from the negative terminal to the positive terminal through a copper wire or some other conductor. When there is a path that goes from the negative to the positive terminal, you have a circuit, and electrons can flow through the wire.

_

You can attach any type of load, such as a light bulb or motor, in the middle of the circuit. The source of electricity will power the load and the load will perform whatever task it’s designed to carry out, from spinning a shaft to generating light. Electrical circuits can get quite complex, but basically you always have the source of electricity (such as a battery), a load and two wires to carry electricity between the two (vide infra). Electrons move from the source, through the load and back to the source. Moving electrons have energy. As the electrons move from one point to another, they can do work. In an incandescent light bulb, for example, the energy of the electrons is used to create heat, and the heat in turn creates light. In an electric motor, the energy in the electrons creates a magnetic field, and this field can interact with other magnets (through magnetic attraction and repulsion) to create motion. Because motors are so important to everyday activities and because they are, in essence, a generator working in reverse.

_

Magnetic field caused by current loop:


A circular electric current is an electromagnet. The magnetic field-lines form rings around the conductors.

_

_

Two charged conductors-voltage:

Everything connected to one battery terminal acquires the same electrical potential (voltage.) The circuit acts like two separate conductors, one with a positive charge and other with negative causing imbalance of charges.

_

_

Electric field caused by opposite charges:


The two charged wires act like the plates of a capacitor. “Force lines” of e-field spew out of one charged conductor and dive into the other.

_

_

Simple circuit propagating EM energy:


The current gives magnetic fields and voltage gives electrical fields and electrical energy travels in circuit as electromagnetic waves surrounding wires.

__

Electricity vis-à-vis electrical energy:

There is a difference between electricity and electrical energy because Coulombs of electricity are very different from Joules of electromagnetic energy. Energy and charge are two different things, so they cannot both be the electricity. In a simple electric circuit, the electricity flows slowly in a complete circle, while the energy moves differently. The electrical energy flows rapidly across the circuit, going from the source to the load but not returning. The energy does not follow the circular flow of electricity; electricity and electrical energy are two different things. No charges of electricity are gained or lost as the charges circulate within the wires, yet batteries create electrical energy from chemical energy, and light bulbs destroy the electrical energy as they convert it into light. Electrical energy takes a rapid one-way path from battery to bulb and then leaves the circuit as light, while electricity flows slowly around (and around and around) a closed-loop path and none is lost. In a light bulb, charges of electricity flow through the filament and back out again. None are lost. This electricity enters the light bulb through one wire, and the same amount of electricity leaves through the other wire. Yet the energy doesn’t act like this at all; it doesn’t flow through. Instead the light bulb uses up the electric energy: the electrical energy flows one-way: into the bulb via both wires and it’s all transformed into heat and light. The electrical energy doesn’t come back out through the second wire and return to the battery. Two things are flowing: electricity flows in a closed loop, while energy is flowing one-way from source to load.  In an AC system, the charges of electricity move back and forth over a distance shorter than a ten-thousandth of a millimeter. In other words, they sit inside the wires and vibrate. That’s what “Alternating Current” or AC is all about. The electricity does not move forward at all (if it did, that would be a direct current or “DC.”) Yet while these charges of electricity are wiggling back and forth, at the very same time the electrical energy moves forward rapidly. Only the electricity “alternates.” The electrical energy does not; the energy flows continuously forwards as waves. In a DC circuit, the electricity within the wires flows exceedingly slowly; at speeds around inches per minute. At the same time, the electrical energy flows at nearly the speed of light. Electrons in an electric current actually flow quite slowly, at speeds on the order of centimeters per minute. And in AC circuits the electrons don’t really flow at all, instead they sit in place and vibrate. It’s the energy in the circuit which flows fast, not the electrons. The electrons in the wire are the “medium” for waves. And when the electrical energy flies along the wires at the speed of light, the electrons do not follow it. Instead the electrons sit in one place and vibrate. So “electricity” is the charge that flows inside the wires; where a quantity of electrons is a quantity of electricity in coulombs, and where a flow of electricity is called “an electric current” in amperes. In an electric circuit, the flow of the electricity is measured in Coulombs per second (Amperes.) The flow of energy is measured in Joules per second (Watts.) A Coulomb is not a Joule, and there is no way to convert from Coulombs of charge into Joules of energy, or from Amperes to Watts. A quantity of electricity is not a quantity of energy. In an electric circuit containing coils, if we reverse the polarity of voltage while the direction of the flowing electricity remains the same, then the direction of the flowing energy will be reversed. Current same; energy flow reversed? Yes. Also, if we exchange wire connection between positive and negative terminal, current will move in opposite direction but the direction of energy will remain same. A flow of energy does not follow the direction of the flowing electricity. You can know everything about the direction of the electricity within a wire, but this tells you nothing about the direction of the flowing electrical energy. In any electric circuit, the smallest particle of electrical energy is NOT the electron. The smallest particle of energy is the “unit quantum” of electromagnetic energy: it is the photon. Electrons are not particles of EM energy, neither do they carry the energy as they travel in the circuit. Electricity is ‘made’ of electrons and protons, while electrical energy is electromagnetism and is ‘made’ of photons. Electrical energy is electromagnetism; it is composed of an electromagnetic field. On the other hand, the particles of electricity (electrons) flowing within a wire have little resemblance to an electromagnetic field. They are matter. Electricity is not energy; instead it is a major component of everyday matter. In an electric circuit, electrical energy does not flow inside the copper. Instead it flows in the empty air surrounding the wires. In the electric power grid, a certain amount of energy is lost because it flys off into space. This is well understood: electrical energy is electromagnetic waves travelling in the air, and unless the power lines are twisted or somehow shielded, they will act as 60Hz antennas. Waves of 60Hz electrical energy can spread outwards into space rather than following the wires. The power lines can even receive extra 60Hz energy from space, from magnetic storms in Earth’s magnetosphere. Electric energy is gained and lost to empty space while the charges of electricity just sit inside the wires and wiggle. Energy is not electricity.

_

Electromagnetism:

Electromagnetic waves were analyzed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell’s Laws, which unify light, fields, and charge, are one of the great milestones of theoretical physics.

_

A field can be considered a type of energy in space, or energy with position. A field is usually visualized as a set of lines surrounding the body, however these lines do not exist, they are strictly a mathematical construct to describe motion. Fields are used in electricity, magnetism, gravity and almost all aspects of modern physics. Electromagnetism manifests as both electric fields and magnetic fields. Both fields are simply different aspects of electromagnetism, and hence are intrinsically related. Thus, a changing electric field generates a magnetic field; conversely a changing magnetic field generates an electric field. This effect is called electromagnetic induction, and is the basis of operation for electrical generators, induction motors, and transformers.

_

Electromagnetic radiation (EM radiation or EMR) is a form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space. EMR has both electric and magnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In vacuum, electromagnetic radiation propagates at a characteristic speed, the speed of light. Energy carried by EM waves is divided 50-50 between electrical and magnetic field i.e. 50 % energy in electrical field and 50 % energy in magnetic field.

_


_

Electromagnetic radiation is a particular form of the more general electromagnetic field (EM field), which is produced by moving charges. According to Maxwell’s equations, a spatially varying electric field causes the magnetic field to change over time. Likewise, a spatially varying magnetic field causes changes over time in the electric field. In an electromagnetic wave, the changes induced by the electric field shift the wave in the magnetic field in one direction; the action of the magnetic field shifts the electric field in the same direction. Together, these fields form a propagating electromagnetic wave, which moves out into space and never again affects the source. The EM field formed by this mechanism “radiates,” hence the term for it. In classical physics, EMR is considered to be produced when charged particles are accelerated by forces acting on them. Electrons are responsible for emission of most EMR because they have low mass, and therefore are easily accelerated by a variety of mechanisms. Rapidly moving electrons are most sharply accelerated when they encounter a region of force, so they are responsible for producing much of the highest frequency electromagnetic radiation observed in nature. Any electric charge that accelerates, or any changing magnetic field, produces electromagnetic radiation. When any wire (or other conducting object such as an antenna) conducts alternating current, electromagnetic radiation is propagated at the same frequency as the electric current. EMR is classified according to the frequency of its wave. The electromagnetic spectrum, in order of increasing frequency and decreasing wavelength, consists of radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

__


_

Is electrical energy similar to light?

Yes.

The seven things below are exactly the same, only their frequency is different.

X-rays

Light

Microwaves

Radio signals

Telephone signals

50 or 60Hz energy from Electric company generators (AC power)

DC energy from batteries

_

Power lines carry the same “stuff” as above, but the frequency is even lower, it is 60 cycles per second (50Hz in Europe & India.) And batteries produce the same “stuff”, but the frequency in that case is near zero. Electrical energy is also called “electromagnetic energy” or “EM energy” or “electromagnetic vibrations.” Electrical energy is a type of wave energy, and these energy-waves always move very quickly (they usually move at the speed of light.) When you turn on a wall switch, the light bulbs light up instantly because the electrical energy moves so fast. Electrical energy is a combination of two things: magnetic fields and electrostatic fields. Electrical energy can be guided by wires, but also it can travel through space without any wires. For example, if we wave a bar magnet near a coil of wire, electrical energy produced by the moving magnet will leap into the coil even though the magnet did not touch the coil. Another example: if we build an antenna that’s about 5000 miles long, we can plug it into an AC wall outlet, and the electrical energy will be broadcast into space and lost. There is no basic difference between “radio signals” and “AC Power”, only their frequency is different.

_

There are TWO main things that flow along wires:

1. Electric Charge:

Charge is a “stuff” that flows through lightbulbs, and it flows around a circuit. Normally no charge is lost during the operation of a circuit, and no charge is gained. Also, charge flows very slowly, and it can even stop flowing and just sit there inside the wires. In an AC circuit, charge does not flow forwards at all; instead it sits in one place and wiggles forwards and back.

2. Electric Energy:

It’s also called “electromagnetic energy”. It always flows very fast; almost at the speed of light. It can be gained and lost from circuits, such as when a light bulb changes the flow of electrical energy into a flow of light and heat.

_

The table below shows difference between two things that flow in an electricity wire, the charge and the energy.

 

ELECTRIC CHARGE

E.M. ENERGY

Flows very slowly, and can even stop.

—–

Always flows incredibly fast, almost at the speed of light.
The flow is called “electric current,” measured in Amps.

—–

The flow is called “electric power,” measured in Watts.
Flows through light bulbs

Consumed by light bulbs (and converted into light)
In AC cables, it wiggles back and forth

In AC cables, it flows continuously forwards
Supplied by metals (and by all other conductors)

Supplied by generators, batteries, etc.
It’s a component of matter

A form of energy
Doesn’t usually leave a circuit.

A “Source” injects it into a circuit, while a “load” removes it again.
Composed of movable charges from conductor atoms

Composed of electromagnetic fields
Electrons and protons are particles of charge.

Photons are particles of E.M. energy. It is same as light and radio waves but lower in frequency.
Flows inside of wires

Flows in the space adjacent to wires
Generators pump it through themselves

Generators create it
Circular flow. It flows around and around the circuit, and never leaves it.

One-way flow, from a “source” to a “load”.
Visible: it is the silvery part of a metal

Invisible: the EM energy can only be seen if you use iron filings, etc.
Measured in units called Coulombs and its flow is measured in Amperes1 ampere = 1 coulombs per second

Measured in units called Joules1 watt = 1 joule per second
Occurs naturally

Produced and sold by electric companies
Scientists called it “electricity.”

Today, electric companies call it “electricity.”

_

One way to interpret the statement “electricity is another form of magnetism” (or vice versa) is through special relativity. If I look at a classical stationary electric charge, it sets up a purely electric field – the Coulomb field, which is responsible for generating the phenomena of static electricity. However, if I now look at this same electric charge, but from the standpoint of a reference frame which is moving with respect to it, what I now see from my new point of view is a moving electric charge, in other words an electric current. An electric current sets up a magnetic field (Ampere’s law). Thus we find the same physical source generating a field which looks like either a magnetic field or an electric field depending upon how you look at it. This transformation between electric and magnetic fields is perfectly described by the Lorentz transformations of special relativity.

_

Electrical circuit:

Electricity travels in closed loops, or circuits. It must have a complete path before the electrons can move. If a circuit is open, the electrons cannot flow. When we switch on light bulb, we are closing the circuit so that electrons can flow.

_


The figure above shows a basic electric circuit. The voltage source V on the left drives a current I around the circuit, delivering electrical energy into the resistor R. From the resistor, the current returns to the source, completing the circuit.

_

An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task. The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics.

_

Flow of electric energy in a circuit:

Electrical energy normally doesn’t flow inside of metals. In fact, the joules being sent out by batteries and generators are located in empty space: they take the form of electromagnetic fields surrounding the wires. While a coil can store energy in the magnetic field outside its windings, and while a capacitor can store energy as an electric field in the insulating layer between the metal plates, an electric circuit handles energy a bit differently. As a whole, an electric circuit does both at once: it’s both a coil and a capacitor. It’s a capacitor because an e-field exists between the two halves of a simple circuit at different potentials. And it’s a coil because a magnetic field surrounds each current-bearing wire. The shape of these fields will demonstrate that the EM energy which flows across a circuit is not stuck to individual electrons, nor is it moving along with the slow electrons within the interior of the metal wires. Instead the EM energy flows rapidly through the space surrounding the metal parts of the circuit.

_

Series and parallel circuits:

There are 2 ways to connect multiple devices to a power source (e.g. speakers to power source), series and parallel.

_


In a series circuit (like the example above), the current must flow through one device to get to the next device. This means that the rate of current flow through all devices is the same. The voltage across each device depends on its impedance/ resistance of each device and the current flowing through the circuit. When adding more components in a series circuit, the current flow decreases, if the applied voltage remains constant.

_


In a parallel circuit (like the example above), each device is directly connected to the power source. This means that each device receives the same voltage. The amount of current flowing through each device is dependent on the impedance/ resistance of that particular device. If devices are added to the power source in a parallel configuration, the current demand/flow from the power source increases. When making any connections to any power source you must know the limits of the source, to prevent damage to the source. This means that if you connect too many speakers, in a parallel wiring configuration to the power source as seen in the figure above, it may well be damaged beyond repair.

_

So in a series circuit, the ‘current’ in each device is the same. In a parallel circuit, the ‘voltage’ is the same across each device. Components of an electrical circuit or electronic circuit can be connected in many different ways. The two simplest of these are called series and parallel and occur very frequently. Components connected in series are connected along a single path, so the same current flows through all of the components. Components connected in parallel are connected so the same voltage is applied to each component. A circuit composed solely of components connected in series is known as a series circuit; likewise, one connected completely in parallel is known as a parallel circuit. In a series circuit, the current through each of the components is the same, and the voltage across the components is the sum of the voltages across each component. In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component. The total resistance of resistors in series is equal to the sum of their individual resistances. In parallel circuit, the current in each individual resistor is found by Ohm’s law and to find the total resistance of all components; add the reciprocals of the resistances of each component and take the reciprocal of the sum. Total resistance will always be less than the value of the smallest resistance. If the cells of a battery are connected in parallel, the battery voltage will be the same as the cell voltage but the current supplied by each cell will be a fraction of the total current and if the batteries are connected in series, the voltage will be sum total of voltage of each battery.

_

Consequences of magnetic induction of electrical current:

1. The solenoid:

a. A solenoid is many loops of wire wrapped tightly into the shape of a cylinder

b. When current flows through the wire composing the solenoid the magnetic fields of all the loops add to produce a strong magnetic field

c. The resultant magnetic field resembles the magnetic field of a bar magnet with a north and a south pole

d. Solenoids are used in many electronic devices

_

2. The electromagnet:

a. An electromagnet is basically a solenoid with a ferromagnetic rod (usually made of iron) through it

b. Because of its molecular properties the ferromagnetic rod intensifies the strength of the magnetic field produced by the solenoid

_

Electromagnet:

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off. To concentrate the magnetic field, in an electromagnet the wire is wound into a coil with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. Much stronger magnetic fields can be produced if a “core” of ferromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core increases the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability of the ferromagnetic material. This is called a ferromagnetic-core or iron-core electromagnet. The direction of the magnetic field through a coil of wire can be found from a form of the right-hand rule. If the fingers of the right hand are curled around the coil in the direction of current flow (conventional current, flow of positive charge) through the windings, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the North Pole. Electromagnets are widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment, as well as being employed as industrial lifting electromagnets for picking up and moving heavy iron objects like scrap iron.

_

The figure below shows a simple electromagnet consisting of a coil of insulated wire wrapped around an iron core. The strength of magnetic field generated is proportional to the amount of current.


__

Electric motor:

Electromagnets paved the way for really harnessing the potential of electricity in the first place. The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current. In electrical appliances, the motor moves because the current flowing from your wall socket produces a magnetic field. It’s not the electricity itself powering the motor, but the charge created by the magnet. The force of the magnet creates rotational movement, which means they rotate around a fixed point, similar to the way a tire rotates around an axle. Electromagnets are especially useful when they’re placed on an axis between two stationary magnets. If the electromagnet’s South Pole is situated against the south pole of one stationary magnet and it’s North Pole against the north pole of the other stationary magnet, the electromagnet will rotate until opposite poles line up. This wouldn’t be very helpful, except the polarity of electromagnets depends on the direction of current flow. Pass electric current in one direction, and the magnet’s north pole will be on one side; reverse the current flow, and the north pole will be on the opposite side. In DC motors, a device known as a commutator reverses the direction of flow of electric current. As the poles of the electromagnet flip back and forth, the magnet is able to rotate without interruption. In AC motors, commutator is not required as alternating current itself is changing direction reversing the polarity of poles of electromagnet.

_

Many electromagnets have an advantage over permanent magnets because they can be easily turned on and off, and increasing or decreasing the amount of electricity flowing around the core can control their strength. Modern technology relies heavily on electromagnets to store information using magnetic recording devices. When you save data to the hard drive in your computer, for example, tiny, magnetized pieces of metal are embedded onto a disk in a pattern specific to the saved information. This data started life as binary digital computer language (0s and 1s). When you retrieve this information, the pattern is converted into the original binary pattern and translated into a usable form. So what makes this an electromagnet? The current running through the computer’s circuitry magnetizes those tiny bits of metal. This is the same principal used in tape recorders, VCRs and other tape-based media. Particle accelerators are machines that propel charged particles toward one another at incredibly high speeds in order to observe what happens when they collide. These beams of subatomic particles are very precise and controlling their trajectory is critical so they don’t go off course and damage the machinery. This is where electromagnets come in. The magnets are positioned along the path of the colliding beams, and their magnetism is actually used to control their speed and trajectory.

__

3. Magnetic sensors:

a. Devices can be made that detect and/or amplify the electric fields induced by changing magnetic fields

b. One example is an audio cassette tape

_

4. Transformers: 2 solenoids and mutual inductance:

a. The current flowing through one solenoid will produce a magnetic field which will induce a current to flow in a second, nearby solenoid effectively “transforming” the current of the first solenoid into a current in the second solenoid.

b. Mutual inductance is a measure of how the magnetic fields produced by 2 (or possibly more) solenoids will effect the current produced in the other(s)

c. Mutual inductance depends on the ratio of the number of loops in one solenoid to the number of loops in the other solenoid

_

5. Generators:

Mechanical work is used to produce changing magnetic fields which are then used to “generate” electric current.

__

AC-DC:

_


The figure above shows Alternating Current (green curve) and Direct current (red curve). The horizontal axis measures time; the vertical, current or voltage.

_

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage. In alternating current (AC), the movement of electric charge periodically reverses direction. In direct current (DC), the flow of electric charge is only in one direction. AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal.

_

In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sine wave. Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. In a simple alternating current (AC) circuit consisting of a source and a linear load, both the current and voltage are sinusoidal. If the load is purely resistive, the two quantities reverse their polarity at the same time. At every instant the product of voltage and current is positive; indicating that the direction of energy flow does not reverse.

_

AC power supply frequency:

The frequency of the electrical system varies by country; most electric power is generated at either 50 or 60 hertz. Some countries have a mixture of 50 Hz and 60 Hz supplies, notably Japan. Off-shore, military, textile industry, marine, computer mainframe, aircraft, and spacecraft applications sometimes use 400 Hz, for benefits of reduced weight of apparatus or higher motor speeds.

_

 Why we use AC at 50 or 60 Hertz:

Going much below 50Hz would cause incandescent lights to flicker. The threshold for humans to perceive such flicker is typically about 16Hz, though it can be detected at higher frequencies by some people. If the frequency is increased substantially, inductive loads become very high impedance, requiring higher voltages to drive the same amount of current. Considering motors (which are inductive loads) use something like half the world’s electricity supply, this would be a bad thing. Also, transmitting them across large distances becomes a problem due to the effects of inductance of long lines. Further, higher frequencies require generators (with a given number of poles) to rotate faster. Going too high increases wear and tear, in addition to adding mechanical instability. The 50 to 60Hz region provides a good compromise. Why 60Hz is used in some parts of the world (primarily USA) while 50Hz is used in others is because of historical artifacts that are not really cost effective to remedy. That said higher frequencies allow the use of lighter transformers and smaller motors and lower frequencies reduce inductive effects over long lines. Higher frequencies (such as 400Hz) are used for specialized purposes (such as in aircraft, where weight is important and you don’t have to worry about long lines) and lower frequencies are used in some railway traction systems.

_


_

Figure above is a graph of the voltage produced by a generator as a function of time. Let’s assume that this happens to be a 120-volt, 60-Hz generator as in US. The voltage at one point in the cycle momentarily passes through 0 volts, but it’s headed for a maximum of 169.7 volts. After that point, the voltage declines, passing through 0 volts, then reverses its polarity, and has a negative “peak” of -169.7 volts. This curve is known as a sine wave since the voltage at any point is proportional to the sine of the angle of rotation. The magnet is rotating 60 times a second, so the sine wave repeats at the same frequency, making the period of a single cycle one-sixtieth of a second. Electrical engineers state the voltage of an AC sine wave as the RMS (root-mean-square), a value equal to the peak value of the sine wave divided by the square root of two, which is approximately 1.414. If you know the RMS voltage, you can multiply it by the square root of two to calculate the peak voltage of the curve. If you were to power a light bulb from 120V (RMS) AC, you would get the same amount of light from the bulb as you would by powering it from 120V DC. Direct current does not change directions– the electron flow is always from the negative pole to the positive pole– Alternating current does change direction– standard household electricity is alternating current, because of its flexibility in traveling long distances. It changes direction at a specific frequency– 60 times per second, or 60 Hz in the United States & Japan, and in Europe & India the standard is 50 Hz.

__

3 Phase Electricity Generation:
At the power station, an electrical generator converts mechanical power into a set of alternating electric currents, one from each electromagnetic coil or winding of the generator. The currents are sinusoidal functions of time, all at the same frequency but with different phases. In a three-phase system the phases are spaced equally, giving a phase separation of 120°.

_


_

The figure above shows one voltage cycle of a 3-phase electrical system, labeled 0 to 360° along the time axis. The plotted line represents the variation of instantaneous voltage (or current) with respect to time. This cycle will repeat 50 or 60 times per second, depending on the power system frequency. 3 phase electricity systems may or may not have a neutral wire. A neutral wire allows the three phase system to use a higher voltage while still supporting lower voltage single phase appliances. In high voltage distribution situations it is common not to have a neutral wire as the loads can simply be connected between phases (phase-phase connection). Colors used may adhere to old standards or to no standard at all, and may vary even within a single installation.

__

Why 3 phase in the first place:

The power plant produces three different phases of AC power simultaneously, and the three phases are offset 120 degrees from each other. There are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three. If you were to look at the three phases on a graph, they would look like this relative to ground: There is nothing magical about three-phase power. It is simply three single phases synchronized and offset by 120 degrees. Why three phases? Why not one or two or four? In 1-phase and 2-phase electricity, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. Also, in three-phase systems the three currents are equal in magnitude and have 120 degrees phase difference while in 2-phase system would have unequal currents. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Three similar coils having mutual geometrical angles of 120 degrees create the rotating magnetic field in three phase motors. The ability of the three-phase system to create a rotating field, utilized in electric motors, is one of the main reasons why three-phase systems dominate the world’s electrical power supply systems. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point. And what about this “ground” as mentioned above? The power company essentially uses the earth as one of the wires in the electricity system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons.

_

There are several reasons why electricity is distributed in three phase:

1.) Polyphase generators can generate more power and cost less to maintain than single phase generators

2.) 3-phase distribution is more efficient than single phase AC

3.) Many industries require 3-phase power

_

Three phase and single phase transmission:

Three-phase electrical generation is very common. The simplest case is three separate coils in the generator stator that are physically offset by an angle of 120° to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other. If coils are added opposite to these (60° spacing), they generate the same phases with reverse polarity and so can be simply wired together. If the load on a three-phase system is balanced equally among the phases, no current flows through the neutral point. For smaller customers (just how small varies by country and age of the installation) only a single phase and the neutral or two phases and the neutral are taken to the property. For larger installations all three phases and the neutral are taken to the main distribution panel. From the three-phase main panel, both single and three-phase circuits may lead off. A third wire, called the bond (or earth) wire, is often connected between non-current-carrying metal enclosures and earth ground. This conductor provides protection from electric shock due to accidental contact of circuit conductors with the metal chassis of portable appliances and tools. Bonding all non-current-carrying metal parts into one complete system ensures there is always a low electrical impedance path to ground sufficient to carry any fault current for as long as it takes for the system to clear the fault. This low impedance path allows the maximum amount of fault current, causing the overcurrent protection device (breakers, fuses) to trip or burn out as quickly as possible, bringing the electrical system to a safe state. All bond wires are bonded to ground at the main service panel, as is the Neutral/Identified conductor if present.

_

230 volt AC:

The usual waveform of an AC power circuit is a sine wave. Consider a 230 V AC mains supply used in many countries around the world. It is so called because its root mean square (RMS) value is 230 V. This means that the time-averaged power delivered is equivalent to the power delivered by a DC voltage of 230 V. To determine the peak voltage (amplitude), we can rearrange the above equation to:

Peak voltage = RMS voltage (230 V) multiply by square root of 2.

For our 230 V AC, the peak voltage is about 325 V.

_

Mains electricity:

_


_

Mains is the general-purpose alternating-current (AC) electric power supply Worldwide for the operation of household and light commercial electrical appliances and lighting. The different countries have different systems are primarily characterized by their Voltage; Frequency; Plugs and sockets (receptacles or outlets); Earthing system (grounding); and Protection against overcurrent damage (e.g., due to short circuit), electric shock, and fire hazards. All these parameters vary among regions. The voltages are generally in the range 100–240 V (always expressed as root-mean-square voltage). The two commonly used frequencies are 50 Hz and 60 Hz. In most countries, household power is single-phase electric power, with two or three wired contacts at each outlet. The live wire (also known as phase, hot or active contact), carries alternating current between the power grid and the household. The neutral wire completes the electrical circuit by also carrying alternating current between the power grid and the household. The neutral is staked into the ground as often as possible, and therefore has the same electrical potential as the earth. This prevents the power circuits from rising beyond earth, such as when they are struck by lightning or become otherwise charged. The earth wire or ground connects cases of equipment to earth ground as a protection against faults (Electric Shock). Circuit breakers and fuses are used to detect short circuits between the live and neutral wires, or the drawing of more current than the wires are rated to handle to prevent overheating and fire. These protective devices are usually mounted in a central panel in a building, but some wiring systems also provide an over current protection device at the socket or within the plug.

_

Europe and most other countries in the world use a voltage which is twice that of the US. It is between 220 and 240 volts, whereas in Japan and in most of the Americas the voltage is between 100 and 127 volts. Originally Europe was 120 V too, just like Japan and the US today. It has been deemed necessary to increase voltage to get more power with less losses and voltage drop from the same copper wire diameter. Note that currently all new American buildings get in fact 240 volts split in two 120 between neutral and hot wire. Major appliances, such as virtually all drying machines and ovens, are now connected to 240 volts. Mind, Americans who have European equipment shouldn’t connect it to these outlets. Although it may work on some appliances, it will definitely not be the case for all of your equipment.

_

Power loss in transmission:

The power losses in a conductor are a product of the square of the current and the resistance of the conductor, described by the formula


This means that when transmitting a fixed power on a given wire, if the current is doubled, the power loss will be four times greater. The power transmitted is equal to the product of the current and the voltage (assuming no phase difference); thus, the same amount of power can be transmitted with a lower current by increasing the voltage. It is therefore advantageous when transmitting large amounts of power to distribute the power with high voltages (often hundreds of kilovolts). AC voltage may be increased or decreased with a transformer. Such arrangement will lessen power loss in transmission as current is low.

_

A direct current flows uniformly throughout the cross-section of a uniform wire. An alternating current of any frequency is forced away from the wire’s center, toward its outer surface. This is because the acceleration of an electric charge in an alternating current produces waves of electromagnetic radiation that cancel the propagation of electricity toward the center of materials with high conductivity. This phenomenon is called skin effect. At very high frequencies the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths. Since the current tends to flow in the periphery of conductors, the effective cross-section of the conductor is reduced. This increases the effective AC resistance of the conductor, since resistance is inversely proportional to the cross-sectional area. The AC resistance often is many times higher than the DC resistance, causing a much higher energy loss due to ohmic heating (also called I2R loss). So in a nutshell, high voltage low frequency AC current is best for reducing transmission loss.

_

Note: The skin depth is the thickness at which the current density is reduced by 63%. Even at relatively low frequencies used for power transmission (50–60 Hz), non-uniform distribution of current still occurs in sufficiently thick conductors. For example, the skin depth of a very thick copper conductor is approximately 8.57 mm at 60 Hz, so high current conductors are usually hollow to reduce their mass and cost. It is not very important for thin household wires at 60Hz. So in DC circuits and in 60Hz AC circuits, the current exists practically all through the entire wire. So Skin Effect only works for very thick wires or for high frequency AC. At extremely high frequencies, the charges in a thin “skin” on the surface of large wires are the charges which move. For circuits involving high-current and high-frequency such as radio transmitters, it makes sense to use copper pipes as conductors. All the charge flow is on the surface of the conductors, so use inexpensive hollow conductors.

_

Why household electrical outlets are AC?  Why not DC?

AC and DC are not that different. If your electric outlets were DC then light bulbs and electric heaters would still work fine. Many motors would still work. So what’s the big deal?

_

DC motors require sliding brushes. Unfortunately, carbon brushes wear out. If your fridge, fans and furnace contained DC motors, you’d have to open them up about once a year to replace the worn brushes. This would be even more inconvenient than replacing light bulbs. But what if someone invented a special kind of motor which never needed new brushes? Nikola Tesla solved the problem by inventing the magnetic vortex motor (commonly known as the AC Induction motor.) These motors have no brushes to reverse the current. Instead they rotate because a magnetic vortex pulls them along. However, these motors require AC. Their operation is based on AC electrical waves. If you never want to replace motor brushes, then you need AC outlets to run all of your brushless “Tesla motors.” Also, Nikola Tesla discovered how to make cross-country electrical grids possible. If electric companies use AC, then there is a simple way to greatly reduce the electrical friction in every cross-country power line. Just transport the energy at low current and extremely high voltage. It’s easy to change low-voltage AC into high voltage. Just use a “transformer”; a pair of electromagnet coils. But Transformers require AC. If DC was used, then either the cross-country power lines would be too expensive (they’d have to be immensely thick cables,) or the electric generators would have to be built right in your neighborhood. With DC, cities would need thousands of small generators instead of one huge generator at a dam or nuclear plant. But why does AC make a difference? It’s because electrical energy is made of voltage and current, but only the current can waste energy by heating up the cross-country power lines. If we could convert the energy into high voltage and low current, then we could send it across hundreds of miles of thin wire, and the electrical friction of the copper metal wouldn’t absorb all the energy. Unfortunately, electrical generators can’t directly produce a high enough voltage. However, there is a simple device which can. It’s called the AC Transformer, and it can convert low voltage electrical energy into high voltage electrical energy. At the same time, it converts high current into low current. If “transformers” are used on both ends of a long power line, then that power line can be hundreds of miles long, yet most of the electrical energy won’t be absorbed by the copper. But transformers only work on AC. They can’t change the voltage of DC. And so electric companies use Tesla’s patents: low voltage generators with transformers and high-voltage transmission lines. If we had some other simple way of stepping the voltage and current up and down, then maybe we could use DC instead. DC works fine for running motors, heaters, and light bulbs. But if you want to send electrical energy through very long wires, you need the AC so you can convert it into high voltage at low current.  Some people do use DC electrical outlets. Boats and campers frequently have them. People living “off the grid”, using solar or hydro power, often use DC instead of AC. These people have nearby generators, so they don’t have to send energy through very long power lines. Some appliances aren’t compatible with both AC and DC, so anyone who has DC outlets instead of AC outlets usually has to buy an entire set of DC-only appliances. Also, some electric companies use DC cross-country power lines. They do this because high voltage DC has less energy loss than the equivalent AC energy. (You see, high voltage DC works better, it’s just very hard to create it.) Electric companies use gigantic expensive transistor devices to convert DC into AC and AC into DC. They mostly use these specialized DC high voltage systems for very long cross-country transmission lines, and also to connect between statewide AC power grids.

_

So in a nutshell, the reasons why AC is used more than DC is as follows:
Firstly, the output of power stations comes from a rotary turbine, which by its nature is AC and therefore requires no power electronics to convert to DC. Secondly it is much easier to change the voltage of AC electricity for transmission and distribution. Thirdly the cost of plant associated with AC transmission (circuit breakers, transformers etc) is much lower than the equivalent of DC transmission. AC generators cost less and can produce more power than an equivalent size DC generator. AC in general is easier to distribute because very efficient transformers can be used to step up and step down distribution voltage. The step up helps reduce distribution losses by substantially reducing the electrical current animation carried by the long distance lines. The voltage on high tension transmission lines may range anywhere between 230kV to as much as 500kV with currents up to 450 Amperes. Transmitting that amount of power at low voltage (240 volts) would mean extremely high currents resulting in unacceptably high ohmic losses. AC transmission provides a number of technical advantages. When a fault on the network occurs, a large fault current occurs. In an AC system this becomes much easier to interrupt, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt. It is also easier to meter AC connections, to monitor power flows across a network.

_
Sometimes DC transmission preferred over AC transmission:

DC transmission however, is used to link two completely different AC systems. An AC link would require the two systems to be entirely in synchrony, with the peaks and troughs of the AC wave to occur at the same time. With a DC transmission link, this can be negated allowing the link of, for example, the UK and European transmission network. Also, in some cases, very high voltage lines (upwards of 1MV) actually use DC! It turns out that very long AC runs (hundreds of miles or so) can actually introduce significant radiation losses. The wavelength of 60 Hertz (used in North America) is 5000 Kilometers or about 3000 miles. Even an antenna of 1/10 of a wavelength (300 miles) will radiate quite a bit. Some of the long haul lines on the US West coast between large metropolitan areas run DC.

__

Why two wires are needed? Phase and neutral.

Basically there is only one wire, but it is connected in a circle. All metals are full of movable electrons, so when we connect a wire in a circle, we are forming a kind of “electric drive-belt” which can move inside the wire. The electrons enter from the neutral point on the socket into the appliance and then move towards the phase point in the socket completing a circle of wire. The phase wire and the neural wire are the part of a single wire circle. But household electric outlets have THREE prongs! Yes, but only two of them are used (phase and neutral). The third one is only used for safety purposes.

_

Neutral vis-à-vis ground:

Neutral is midpoint between a positive and a negative. Relative to ground, the potential difference is usually zero, but that is not necessarily true. In power electronics, it may be true only on average, such as in some switched-mode power supplies where the neutral voltage bounces above and below zero, but is zero on average. Ground is generally ‘earth’ or equipment frame or chassis or building iron or a ground rod driven into the ground, and is usually associated with the human safety side of the electrical system. Neutral and ground may be directly connected, or may be connected with an intentional impedance between them. For these circuits, under normal conditions there is no potential difference between neutral and ground.

_

Importance of neutral:

Remember, Electrical power always requires a return path. Think of a battery. If you connect only one lead of a battery to a bulb, nothing happens. You have to connect the other lead of the battery to the other terminal of the bulb, and then current can flow and the bulb will light. In a three phase AC power system, the purpose of the neutral is to carry the imbalance load of the energized conductors back to the source. If the system is completely balanced then there is no current on the neutral. This is because the three phases are balanced – they are of the same magnitude, 120 degrees apart. There is no electrical pressure applied therefore no shock. If there is a slight unbalance between the three, you will see some current in the neutral. A three phase motor does not need a neutral because it has two ‘phase’ leads running it at any given point in time. The electricity comes in on one phase lead and goes out on the other phase lead. On a single phase system, since there is no possibility of balance between the phases, the neutral provides the total return path back to the source. If you’re referring to your home, where you likely have single phase, and have three prong outlets, the neutral should be carrying the return current from the hot wire. This is not to be confused with the ground plug (the round one), which should not be carrying any current. The purpose of this plug is to provide a low resistance path to ground in the event something bad happens (so the current chooses this wire to flow in instead of you). Neutral does not “carry current to ground”. Neutral carries current to some return point, which may or may not be grounded. Neutral, however, is always grounded at some point which, conversely, may or may not be the return point.

_

In India, the home supply is directly single phase 220V with neutral & ground. In the U.S. it’s called split phase, you have 2 lines of 110 each to neutral, with each being out of phase with the other, so between the two hot lines you have 220 volts. To get 220 volts you use the two hot leads. With the two phases and no neutral, the load is supplied with 220V nominal with the phases as returns for each other. Current comes out of one and returns via the other. So there is a “return path,” and you don’t need a neutral to have a “return path.” For 110 volts, current comes out of one of the hot leads and returns via the neutral.

_


_

Since AC power is alternating current reversing direction 50 to 60 times a second, are two wires connected to your appliance interchangeable?  Then why one wire is called neutral? What is ground wire? Why three prongs?

_

Yes, in an Alternating Current system there is no “plus” and “minus,” so in theory the two wires (phase and neutral) should be interchangeable. But in practice, it is different as discussed below.

_

The entire world is a gigantic electrostatic generator. There is a flow of charge going on vertically everywhere on earth. Thunderstorms pump negative charge downwards, and the charge filters upwards everywhere else on earth. Depending on the height of your circuitry above the earth’s surface, depending on the area covered by your wires, and depending on whether there was a thunderstorm above you at the time, there might be a fairly huge DC charge on your electrical distribution system. This charge might be several hundred volts; enough to zap computers and delicate electronics. Or… it might be many tens of thousands of volts, enough to create enormous sparks which jump across switches and leap out of wall outlets, wall switches, across transformer windings, etc. Your electric power system is acting like a sort of capacitive “antenna” which intercepts the feeble current coming from the sky and builds up a huge potential difference with respect to the earth. In addition to the above, you would find an unsettling phenomenon whenever lightning directly strikes your electrical distribution system. The lightning impulse-voltage spreads instantly throughout your whole network, which not only can explode every single appliance plugged in at the time, but can create lethal arcs many feet in length that reach out to “touch” your customers should they be anywhere near those wires within the walls. There is a simple solution to these problems: connect your system to the Earth. Drive some long metal rods into the dirt, and connect them to your wires. That way, lightning currents will be directed into the Earth rather than spreading throughout your power lines. Also, the clear-weather sky current can no longer build up a high voltage, if any excess charge immediately leaks into the earth. Of course you cannot connect BOTH wires to ground, since that would also connect your wires to each other and short out the system. So, you must pick one wire. Connect that wire to ground. So this is so called “neutral” wire of AC current. So basically the neural wire in your home is actually connected to earth right from generator to the grid to your home. One wire of your system is now almost totally safe because it is connected to ground. But the other wire has developed a new hazard, because whenever the occasional customer comes into contact with it, that customer is gets electric shock. By grounding half of your electric network, you’ve accidentally connected one entire half of your network indirectly to everyone’s feet who stand on ground. When someone stands barefoot upon a damp floor, this electrically connects that person into the system. If they touch the grounded (“neutral”) wire in the AC system, nothing happens. But if they touch the other, non-grounded wire (phase), this applies the full AC voltage between their feet and finger. The new unwanted current path within their body may electrocute individual. The solution: guarantee that no one touches the non-grounded wire. Get into the schools and pound into everyone’s mind that AC wires are dangerous. Teach all electricians and technical people that one of the wires is now to be called “Hot”, and that this wire can be lethal if touched. Choose differing colors for the two wires (black is “hot” in the US). Force manufacturers to treat the wires differently inside appliances, designing with careful wire positioning and adding extra insulation to the “hot” wire. For appliances with one wire connected to the metal case, this connects the case to the grounded or “neutral” side instead of to the “hot” side. Things now seem much improved, but there are still problems. If an appliance is dropped into water, and if that water is touching a grounded container (such as a bathtub, a kitchen sink, or even a basement floor or a standing pool outdoors) then any human sticking more than one appendage into the water will be in serious trouble. Another thing: sometimes an appliance with a metal case will suffer internal wear or damage, and then the “hot” wire will wiggle around inside and end up touching the metal case. Anyone standing on wet ground will feel pain and death if they should grab that metal case. So what is the solution?  Add a Third Prong! Connect this prong to the neutral side of the network, but do it only in one place in the circuit, and run a new third wire out to all of the wall-outlets. Give this wire a new color, one which is different from the other two. Give this third prong a very different shape as well, so even Highly Imperfect Electricians will rarely connect the special prong to the wrong wire. And inside all the metal-cased appliances, insist that manufacturers connect this third wire to the case. The idea works! Like magic the faulty metal-cased appliances start blowing their fuses to indicate trouble. And power tools dropped into water will create a current path to the metal case rather than to nearby humans standing in the puddle.

_

So in a nutshell, we have devised three pronged plug and socket for AC connection in your home or office. One of them is the phase, another one is the neutral (ground) and the third one is the safety wire connected in one end to metal cases of all appliances and the other end to the neutral (ground).

_

During the shocking event, some of the AC flowing charge is going in (and out) of the “hot” wire, but it is NOT going back into (and out of) the “neutral” wire as it’s supposed to. Instead, it’s going through the human, and also going into the grounded pipes of the plumbing. If we could measure the current that’s taking the “wrong” path, maybe we could detect the problem and turn off the power before anyone dies. We can’t measure the current in the plumbing, but we can measure it in the “hot” wire, measure the current in the “neutral” wire, and then subtract them. This tells us the value of electric current escaping via the “illegal” path through the human to ground. The subtraction should normally give a zero result, since there never should be a current path to ground that isn’t using the neutral wire. If we amplify the subtraction’s result and use it to trip a circuit breaker, we’ll have a new type of appliance which turns itself off immediately when any human gets into the electrical path. These devices are now required in wet areas of homes (bathrooms.) They’re called Ground Fault Interrupters.

_

What happens if neutral wire is disconnected?

It depends – if a single circuits’ neutral is disconnected then anything downstream will not work – there is no return path for power. It is like switching off a fan. If it is the neutral for a multi-wire circuit (such as the neutral – and ground – connection at the main panel) then you run the risk of creating a voltage imbalance if there are any 220v devices running. That’s because a 120v load is using the other hot leg as a return path – through the 220v device. There are many instances in which office equipment has burned up due to bad connections in a multi-wire power pole.

_

Ground or earth in electricity:

In electrical engineering, ground or earth can refer to the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth. Electrical circuits may be connected to ground (earth) for several reasons. In mains powered equipment, exposed metal parts are connected to ground to prevent user contact with dangerous voltage if electrical insulation fails. Connections to ground limit the build-up of static electricity when handling flammable products or electrostatic-sensitive devices. In some telegraph and power transmission circuits, the earth itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor.

_

The word “ground” means:

  1. A ‘common’ connection, but not connected to Earth.
  2. A direct connection to the power supply (usually to the DC negative terminal)
  3. A connection to the inside of a shielded metal box
  4. A connection to a metal stake driven into the earth (or a connection to a metal water pipe which extends out of the house into dirt.)

Only number four is actually connected to ground! From 1 to 3 are misnomers.

_

How can we convert AC into DC, and vice versa?

To convert AC to DC, we can use an “electrical ratchet” which only allows the charges to move in one direction. These “ratchets” are called Diodes or Rectifiers. They act like a one-way valve for flowing charges in wires. To change the vibrations of AC into one-way DC, just add a diode to the circuit. Or, if you need a device which takes in AC and spits out DC, then hook four diodes together (this is called a “full wave bridge rectifier.)  Converting DC to AC is more difficult. Some sort of “electrical wiggler” is required. The circuit is not simple, and must contain transistors or other types of electronic switching. This type of device is called a “DC to AC inverter.” A power inverter, or inverter, is an electrical device that changes direct current (DC) to alternating current (AC); the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits. Inverters are commonly used to supply AC power from DC sources such as solar panels or batteries. The inverter performs the opposite function of a rectifier.

_

Direct Current (DC) Electricity:

Direct current or DC electricity is the continuous movement of electrons from an area of negative (−) charges to an area of positive (+) charges through a conducting material such as a metal wire. Whereas static electricity sparks consist of the sudden movement of electrons from a negative to positive surface, DC electricity is the continuous movement of the electrons through a wire. A DC circuit is necessary to allow the current or steam of electrons to flow. Such a circuit consists of a source of electrical energy (such as a battery) and a conducting wire running from the positive end of the source to the negative terminal. Electrical devices may be included in the circuit. DC electricity in a circuit consists of voltage, current and resistance.

_


_

Although the negative charged electrons move through the wire toward the positive (+) terminal of the source of electricity, the current is indicated as going from positive to negative. This is an unfortunate and confusing convention.

_

Batteries and DC generators are the sources to create DC electricity. Flash lights and electronic devices such as vacuum tubes, transistors and integrated circuits are usually operated on direct current.

_

Is electricity weightless?

If by ‘electricity’ we mean the electrons, then ‘electricity’ is not weightless. Take a copper wire for example. Each atom weights about 115,000 times larger than the weight of an electron. If each atom supplies one electron to the “electric fluid” sea, then that sea is very light, but it is not weightless. The flowing “electricity” weighs about a hundred thousand times less than the copper metal. It’s like a low pressure gas rather than like a liquid. One Kg of copper would contain about ten milligrams of the movable electron-stuff which can flow as an electric current. If by “electricity” we mean electrical energy, then it is weightless.

__

Spark is plasma:

An electric spark is a volume of air which has been electrically converted from a gas into plasma, the fourth state of matter. While plasma can be created by high temperatures, it can also be created electrically when a high voltage pulls loose the outer electrons of air molecules. Plasma is conductive, so once it has formed between two wires, it joins the wires together electrically, and charges can flow through it. It might seem as if “electricity” has jumped through the air. In reality, a glowing “wire” has formed, and this “wire” is made of plasma. We can only see the plasma jump between the ends of the wires. We cannot see the flowing charges or the electrical energy. Sparks are made of glowing air, and the color of the spark depends on the type of gases involved. Sparks in nitrogen/oxygen are bluish-violet, while sparks in Neon are red/orange. (Yes, the glow inside a neon sign is a kind of fuzzy low-pressure spark.)Also, sparks are conductive. Once formed, they can contain an electric current in much the same way that a wire can. In many ways a spark is like a bit of air which has been turned into an electrical wire. When you watch a thunderstorm, imagine that the clouds are throwing out highly charged wires which will explode if they touch the ground.  Sparks can leap in either direction regardless of polarity, and can leap from either a DC electrode or an AC electrode. They can start on a DC negative electrode and jump towards positive. Or they can start on the positive and go towards the neg. They can even start in the air between two electrodes and spread outwards in both directions. Sparks in air involve avalanches of electrons from the air molecules, but they also involve photons of Ultraviolet light. The strong electrostatic field at the tip of a spark causes nearby air molecules to break apart into separate electrons and ion as a free electron strikes molecules and releases more electrons in an avalanche. Air turns into plasma. But also the electrons captured by atoms can give off ultraviolet photons, and if this light is absorbed by nearby air molecules, it can knock electrons off and spread the plasma that way.

_

Atmospheric electricity:

Atmospheric electricity is the regular diurnal variations of the Earth’s atmospheric-electromagnetic network. The Earth’s surface, the atmosphere and the ionosphere, together are known as the global atmospheric electrical circuit. There is always free electricity in the air and in the clouds, which acts by induction on the earth and electromagnetic devices. Experiments have shown that there is always free electricity in the atmosphere, which is sometimes negative and sometimes positive, but most generally positive, and the intensity of this free electricity is greater in the middle of the day than at morning or night and is greater in winter than in summer. In fine weather, the potential increases with altitude at about 30 volts per foot (100 V/m). The phenomena of atmospheric electricity are of three kinds. There are the electrical phenomena of thunderstorms, the phenomena of continual electrification in the air and the phenomena of the polarauroras.

__


The picture above shows cloud to ground lightning in the global atmospheric electrical circuit. This is an example of plasma present at Earth’s surface. Typically, lightning discharges 30,000 amperes, at up to 100 million volts, and emits light, radio waves, x-rays and even gamma rays. Plasma temperatures in lightning can approach 28,000 kelvins and electron densities may exceed 1024/m3.

_

Lightning is a massive electrostatic discharge caused by unbalanced electric charge in the atmosphere. Lightning can be either inside clouds (IC), cloud to cloud (CC) or cloud to ground (CG) and is accompanied by the loud sound of thunder. Because the speed of sound in air (~340 m/s) is so much slower than the speed of light (300,000,000 m/s) from the lightning flash, the distance to a lightning strike can be closely approximated by dividing the flash-thunder interval. They usually occur during a heavy rainstorm or thunderstorm. Turbulence in storm clouds creates static electric charges that build up until they are released as a stream of electrons that create a bolt of lightning. Air is super-heated until it glows white hot and creates a shock wave that is the sound of thunder. Lightning usually originates in turbulent storm clouds that reach high into the atmosphere, where raindrops are both frozen into ice particles or remain as super-cooled water. The droplets of ice and rain become electrically polarized as they fall through the atmosphere’s natural electric field. That means that one side of the droplet or ice particle has a positive (+) electrical charge and the other side has a negative (−) charge. When these polarized raindrops and ice particles come close to each other or collide, they become charged by electrostatic induction. The smaller particles gain positive electrical charges and larger particles gain negative charges. The turbulence and updrafts in the storm cloud cause the lighter ice particles to move upwards. This results in the area near the top of the cloud to accumulate positive charges. The heavier ice particles and hail fall towards the middle and lower parts of the cloud, building up negative charges in those areas. When the electrical potential difference between the positive charges near the top of a cloud and the negative charges near the middle or bottom of the cloud is great enough, the electrical field causes the air to ionize, breaking down its resistance and allowing the spark or lightning bolt to jump across the air gap. This potential energy is measured in voltage and can be from 10,000,000 volts to over 100,000,000 volts. The release of this energy causes the stream of electrons to superheat the air to about 50,000°F or 28,000°C. The air then becomes incandescent and turns white-hot. The heat causes the air to rapidly expands creating a sonic boom, similar to the noise made by an aircraft flying at supersonic speeds. The sonic boom is the crashing sound of thunder that you hear. Research has shown that aircraft rarely are struck by lightning when aircraft fly between oppositely charged parts of a thunderstorm , instead the aircraft themselves do the striking, since the plasma starts on the wingtips and zips outwards, striking the clouds. Lightning can seriously damage trees, houses and other structures that it strikes. The high temperature of a lightning bolt can easily set a building on fire. The force of a lightning bolt can shatter the trunk of a tree. The extremely high voltage of a lightning bolt can cause metal to melt. If lightning strikes someone, it can easily kill the person. There are about 60 deaths a year in the United States due to lightning strikes. Cambodia has a much higher fatality rate, with 75 people being killed in 2008. Lightning strikes injure about 1000 people in the U.S. each year.

_

Benefits from lightning:

The greatest benefit of lightning is that it separates Nitrogen from the air, providing natural fertilizer to the ground below. Each year, 10 million tons of nitrogen is deposited into the Earth. Lightning also causes forest fires which are essential in rejuvenating the forests and getting rid of old growth.

_

Electricity misconception:

1. We do not study “electricity”; we study “electrical science.”

2. Generators don’t produce “electricity”; they produce “electrical energy” which is made of invisible fields resembling radio waves that whiz along outside of the wires. Generators are charge pumps. They force the charges found inside the wires to flow along.

3. “Electricity” doesn’t flow inside metal wires, charges do.

4. Batteries don’t supply “electricity”, the wires do. A battery is a chemically-fueled charge pump. Like any other pump, a battery takes charges in through one connection and spits them out through the other. A battery is not a source of the charges being pumped, the wire is the source of charge (free electrons). When a battery runs down, it’s because its chemical fuel is exhausted, not because any charges have been lost. When you “recharge” a battery, you are pumping charges through it backwards, which reverses the chemical reactions and converts the waste products back again into chemical fuel.

5. Light bulbs don’t consume “electricity.” Instead, the charges of the thin filament are forced to flow along much faster than they would in thicker wires, and this heats the filament because of a sort of “electrical friction”. Charges are flowing into the bulb through one terminal, but then they flow back out again through the other terminal. The quantity of charges inside the filament doesn’t change, and none are used up.

6. Avoid saying “static electricity” and “current electricity”. Instead call them “charge imbalance” and “charge flow”, or possibly “voltage” and “current”. (A little known fact: static electricity involves high voltage. Also, even the flowing charges during electrical currents will always display the familiar “static electricity” effects whenever the voltage is high.)  7. Even avoid saying “Current flows”. After all, current doesn’t flow in wires; charges do. Since the term Electric Current means the same thing as charge-flow, just simplify the concept by talking exclusively in terms of charge-flow.

_

Electricity generation:

_

The electrical battery store energy chemically and make it available on demand in the form of electrical energy. The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines. Electrical power is usually generated by electro-mechanical generators driven by steam produced from fossil fuel combustion, or the heat released from nuclear reactions; or from other sources such as kinetic energy extracted from wind or flowing water; or gravitational potential energy at a Dam. Environmental concerns with electricity generation have led to an increased focus on generation from renewable sources, in particular from wind and hydropower. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean. Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required. This requires electricity utilities to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. A certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses.

_

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge (usually carried by electrons) to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow (but does not create water). The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

_

Electricity generation is the process of generating electric energy from other forms of energy. The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of a loop of wire, or disc of copper between the poles of a magnet. Electricity is most often generated at a power station by electromechanical generators, primarily driven by heat engines fueled by chemical combustion or nuclear fission but also by other means such as the kinetic energy of flowing water and wind. There are many other technologies that can be and are used to generate electricity such as solar photovoltaics and geothermal power.

_


The animation above shows AC power generator.

_

Electric generator:

The basic electric generator uses a set-up similar to the electric motor but in this case one does not send a current through the wire loop, but instead rotates it in the magnetic field. This rotation comes from the action of falling water (in a hydroelectric plant) or steam (in a coal or nuclear power plant) hitting turbine blades, causing them to turn. A changing magnetic field subsequently is established through the plane of the wire loops, which causes a current to be generated. In this way mechanical or rotational energy is converted to electrical energy. It turns out that as the loop rotates through one complete revolution the direction of the current reverses, which is an AC current.

_

You can generate electricity by many methods without magnetic fields: chemical (batteries and fuel cells), solar (photovoltaic cells), and thermal (thermocouples, Seebeck effect). There are many biological generators as well (nerve and muscle tissues in your body) in addition to the obvious electric eels. You can generate electricity by rubbing your hands together… or more efficiently by rubbing cat furr on glass. Any sort of rubbing causes electrons to move and starts a chain reaction called electricity.

_

Can generator work without magnet?

Yes. The field and the armature are both windings on a laminated iron core. The field is an electromagnet driven by the generator’s own output. This is probably rectified and adjusted to perform regulation. This task is often achieved using SCRs, a type of gated rectifier. How does it get going? There is usually a small residual magnetism in the field or armature, enough that it makes a small voltage. This is rapidly built to the full output. That is why a generator can need “flashing”, when it refuses to start because there is no residual field.The field is connected to a battery etc so that a residual is left again, then you can get it going. Incidentally the field is normally about 1/10 the power of the output.

_

Methods of generating electricity:

There are seven fundamental methods of directly transforming other forms of energy into electrical energy:

_

1. Static electricity, from the physical separation and transport of charge (examples: triboelectric effect and lightning)

2.Electromagnetic induction, where an electrical generator, dynamo or alternator transforms kinetic energy (energy of motion) into electricity, this is most used form for generating electricity, it is based on Faraday’s law, can be experimented by simply rotating a magnet within closed loop of a conducting material (e.g. Copper wire)

3. Electrochemistry, the direct transformation of chemical energy into electricity, as in a battery, fuel cell or nerve impulse

4. Photoelectric effect, the transformation of light into electrical energy, as in solar cells

5. Thermoelectric effect, direct conversion of temperature differences to electricity, as in thermocouples, thermopiles, and thermionic converters.

6. Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. Researchers at the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal display using thin films of M13 bacteriophage .

7. Nuclear transformation, the creation and acceleration of charged particles (examples: betavoltaics or alpha particle emission).

_


_

Turbines:

Most of the electricity in the world is produced in steam turbines. A turbine converts the kinetic energy of a moving fluid (liquid or gas) to mechanical energy. Steam turbines have a series of blades mounted on a shaft against which steam is forced, thus rotating the shaft connected to the generator. In a fossil-fueled steam turbine, the fuel is burned in a furnace to heat water in a boiler to produce steam. In a nuclear steam turbine, the heat from the fission of uranium atoms is produced in a reactor vessel heat water to produce steam. The electricity generation sequence involves taking charge from the Earth, doing work on it to give it energy (expressed in terms of voltage), transporting the energy via a distribution system, using the energy, and dumping the spent charge back to the Earth. All turbines are driven by a fluid acting as an intermediate energy carrier. Many of the heat engines just mentioned are turbines. Other types of turbines can be driven by wind or falling water. Sources include:

1. Steam – Water is boiled by:

a. Nuclear fission,

b. The burning of fossil fuels (coal, natural gas, or petroleum). In hot gas (gas turbine), turbines are driven directly by gases produced by the combustion of natural gas or oil. Combined cycle gas turbine plants are driven by both steam and natural gas. They generate power by burning natural gas in a gas turbine and use residual heat to generate additional electricity from steam. These plants offer efficiencies of up to 60%.

c. Renewable. The steam generated by:

i) Biomass

ii) Solar thermal energy (the sun as the heat source): solar parabolic troughs and solar power towers concentrate sunlight to heat a heat transfer fluid, which is then used to produce steam.

iii) Geothermal power. Either steam under pressure emerges from the ground and drives a turbine or hot water evaporates a low boiling liquid to create vapour to drive a turbine.

iv) Ocean thermal energy conversion (OTEC): uses the small difference between cooler deep and warmer surface ocean waters to run a heat engine (usually a turbine).

2. Other renewable sources:

a. Large dams such as Hoover Dam can provide large amounts of hydroelectric power; it has 2.07 GW capability. Water (hydroelectric) – Turbine blades are acted upon by flowing water, produced by hydroelectric dams or tidal forces.

b. Wind – Most wind turbines generate electricity from naturally occurring wind. Solar updraft towers use wind that is artificially produced inside the chimney by heating it with sunlight, and are more properly seen as forms of solar thermal energy.

_

Electricity production in 2008 from various resources worldwide:


_

The above figure depicts that more than 80% of our electricity comes from the fossil fuels and nuclear that the Greens despise. Hydroelectricity, with all its pluses and minuses, produces a serious 16% of the total. But all the vanity renewables bundled together make about 2 to 3.5% of the total. Wind power is a major global industry but it’s only making in the order of 1.4% of total electricity. And solar is so pathetically low that it needs to be bundled with “tidal and wave” power to even rate 0.1% (after rounding up). CFor all the fuss and money, if the world’s solar powered units all broke tonight, it would not dent global electricity production a jot. No one connected to a grid would notice. So the bad guys fossil fuel and nuclear power actually runs the world.

_

Power from fossil fuel:

Coal, petroleum (oil), and natural gas are burned in large furnaces to heat water to make steam that in turn pushes on the blades of a turbine.

_

Coal:

Coal is cheap and abundant, with an estimate of over 200 years supply of economic coal deposits still accessible, which is why we are still using so much of it, despite the high levels of pollution and greenhouse gas emissions it produces. Coal plays a vital role in electricity generation worldwide. Coal-fired power plants currently fuel 41% of global electricity. In some countries, coal fuels a higher percentage of electricity. Steam coal, also known as thermal coal, is used in power stations to generate electricity. Coal is first milled to a fine powder, which increases the surface area and allows it to burn more quickly. In these pulverized coal combustion (PCC) systems, the powdered coal is blown into the combustion chamber of a boiler where it is burnt at high temperature. The hot gases and heat energy produced converts water – in tubes lining the boiler – into steam. The high pressure steam is passed into a turbine containing thousands of propeller-like blades. The steam pushes these blades causing the turbine shaft to rotate at high speed which is connected to generator.

_

What are the advantages and disadvantages of using coal to generate electricity?

Some of the advantages of coal are –

1.Easily combustible, and produces high energy upon combustion helping in locomotion and in the generation of electricity and various other forms of energy; [ Note: actually, in terms of J/kg of energy, coal is one of the lowest energy density common fuels – about 50% more than wood, but half that of natural gas or oil]

2. Widely and easily distributed all over the world; [ Note: coal is simple and easy to ship, but major deposits are heavily concentrated in relatively few locations]

3. Good availability – relatively large existing reserves

4. Relatively inexpensive – extraction is rather straightforward and shipping/handling is much simpler than other types of fossil fuels

5. While mining can be moderately dangerous, after extraction, coal is much safer to ship and handle (provided a few precautions are taken) than other fossil fuels, and requires little or no special handling.

6. A coal-fueled power station can be built almost anywhere, so long as you can get large quantities of fuel to it. Most coal fired power stations have dedicated rail links to supply the coal.

_

However, the important issue as of now is whether there are more disadvantages than advantages of fossil fuels like coal!
Some disadvantages of coal are that –

1. It is Nonrenewable and fast depleting;

2. High coal transportation costs, especially for countries with no coal resources and hence will require special harbors for coal import and storage.

3. Coal storage cost is high especially if required to have enough stock for few years to assure power production availability.

4. Burning fossil fuels releases carbon dioxide, a powerful greenhouse gas, that had been stored in the earth for millions of years, contributing to global warming. Coal in particular is much “dirtier” than other forms of fossil fuels and releases considerably more CO2, NO, SO2 and other gaseous byproducts than oil or natural gas

5. It leaves behind harmful byproducts upon combustion, thereby causing a lot of pollution – both particulate matter (as part of the exhaust), and residual ash from the burned coal.

6. Mining of coal leads to irreversible damage to the adjoining environment;

7. Mining and burning of coal pollutes the environment, causes acid rain and ruins all living creature’s lungs.

8. It cannot be recycled.

9. Prices for all fossil fuels are rising, especially if the real cost of their carbon is included.

10. An average of 170 pounds of mercury is made by one coal plant every year. When 1/70 of a teaspoon of mercury is put in to a 50-acre lake it can make the fish unsafe to eat.

11. Coal power puts the lives of the people who dig the coal in danger, and it gives them poor lung quality.

12. A coal plant generates about 3,700,000 tons of carbon dioxide every year; this is one of the main causes of global warming.

13. A single coal plant creates 10,000 tons of sulfur dioxide, which causes acid rain that damages forests, lakes, and buildings.

14. When people dig for coal, they cut down many trees.

15. A coal plant also creates 720 tons of carbon monoxide; which causes headaches and place additional stress on people with heart disease.

16. A 500-megawatt coal- fired plant draws about 2.2 billion gallons of water from nearby bodies of water. This is enough water to support approximately 250,000 people.

_

Natural gas:

Natural gas (methane) is a fossil fuel. It is a gaseous molecule that’s made up of two atoms – one carbon atom combined with four hydrogen atom. Its chemical formula is CH4. The picture below is a model of what the molecule could look like. Don’t confuse natural gas with “gasoline,” which we call “gas” for short. LPG, or liquefied petroleum gas, is made up of methane and a mixture with other gases like butane. CNG means compressed natural gas.

_


_

Natural gas, in addition to being burned to heat water for steam, can also be burned to produce hot combustion gases that pass directly through a turbine, spinning the blades of the turbine to generate power. Gas turbines are commonly used when power utility usage is in high demand. In 2000, 16% of the America’s power was fueled by natural gas.

_

Natural gas can be used to generate electricity in a variety of ways. The most basic natural gas-fired electric generation consists of a steam generation unit, where fossil fuels are burned in a boiler to heat water and produce steam that then turns a turbine to generate electricity. Gas turbines and combustion engines are also used to generate electricity. In these types of units, instead of heating steam to turn a turbine, hot gases from burning fossil fuels (particularly natural gas) are used to turn the turbine and generate electricity. Many of the new natural gas fired power plants are known as ‘combined-cycle’ units. In these types of generating facilities, there is both a gas turbine and a steam unit, all in one.

_

Natural gas offers a number of significant environmental benefits over other fossil fuels. Largely a result of its chemical simplicity, it is the cleanest burning of all fossil fuels. Natural gas is primarily composed of methane, with most of the impurities removed by gas processing at the field and gas plant. When combusted, the main products of combustion are CO2, water vapor and small amounts of NO2 and SO2. Coal and oil, by contrast, are composed of much more complex molecules, with a higher carbon ratio and higher nitrogen and sulfur contents. This means that when combusted, coal and oil release higher levels of harmful emissions, including nitrogen oxides (NO2), SO2, CO2, carbon monoxide (CO), and other hydrocarbons. In addition, coal and fuel oil release ash particles – particles that do not burn – into the environment. Electricity generation is the main nonresidential use of natural gas. Globally, there is an increasing demand for electricity, coupled with reduced tolerances for nuclear and hydro plants, tightening limits on air, water, and noise pollution emissions, as well as high cost for wind and solar energy. This leaves gas-fired generation as one of the only remaining options for electrical utility companies. Because the cost of fuel accounts for around 65% of the cost of electricity, the choice of fuel is an important decision for power plant developers. Coal remains the dominant fuel for the world’s thermal electric power plants. Coal has been the main thermal electric fuel due to its cheap price, worldwide availability, easy transport, and low-technology threshold. However, as stated above, Coal’s biggest drawback is the pollution emitted from its combustion. Modern gas-fired power plants are much cleaner and more efficient than their predecessors. They are also larger, cheaper to build, less noisy, less polluting, and easier to switch on and off. In addition, obtaining permits to build gas-fired plants is usually much easier than an equivalent coal or nuclear plant for these reasons. On a full cost (including fuel as well as capital depreciation costs) basis, gas is more expensive than existing nuclear power generation, but significantly cheaper than coal or renewable power. If environmental costs are added to this analysis, the advantages of gas will be greater.

_

Natural gas as transport fuel:

Natural gas in the form of compressed natural gas (CNG), which is basically methane gas pressured to 200 bar to 250 bar, is an ideal transportation fuel. LPGs are also commonly used transport fuels. Natural gas holds the greatest promise as a fuel for fleet vehicles that refuel at a central location, such as transit buses, short-haul delivery vehicles, taxis, government cars, and light trucks. There are currently approximately 65,000 natural gas vehicles (NGVs) in operation in the United States using CNG and LPG as their main fuels. There are an estimated 10 – 20 million vehicles around the world that use CNG and LPG as their primary fuel. Notable countries are (Argentina, Pakistan, Brazil, Italy, India, Iran, US (for CNG) and Italy, Australia and Japan (for LPG vehicles).

_

Residential Gas Markets:

Today, most large cities in North America, Europe, and Northern Asia have extensive natural gas networks supplying residential and commercial consumers with clean and reliable natural gas, primarily for space heating, water heating, and cooking. Many cities in developing countries are also installing local gas pipelines and networks.

_

Petroleum oil:

Petroleum can also be used to make steam to turn a turbine. Residual fuel oil, a product refined from crude oil, is often the petroleum product used in electric plants that use petroleum to make steam. Petroleum was used to generate less than three percent (3%) of all power generated in U.S. power plants in 2000. Three technologies are used to convert oil into electricity:

1. Conventional steam – Oil is burned to heat water to create steam to generate electricity.

2. Combustion turbine – Oil is burned under pressure to produce hot exhaust gases which spin a turbine to generate electricity.

3. Combined-cycle technology – Oil is first combusted in a combustion turbine, using the heated exhaust gases to generate electricity. After these exhaust gases are recovered, they heat water in a boiler, creating steam to drive a second turbine.

_

Nuclear power:

Nuclear power is a method in which steam is produced by heating water through a process called nuclear fission. In nuclear power plants, a reactor contains a core of nuclear fuel, primarily enriched uranium. When atoms of uranium fuel are hit by neutrons they fission (split), releasing heat and more neutrons. Under controlled conditions, these other neutrons can strike more uranium atoms, splitting more atoms, and so on. Thereby, continuous fission can take place, forming a chain reaction releasing heat energy. This energy is used to heat water until it turns to steam. From here, the mechanics of a steam power plant take over. The steam pushes on turbines, which force coils of wire to interact with a magnetic field. This generates an electric current.

_

Sixteen percent of the world’s electricity is supplied by nuclear power, according to the World Nuclear Association. The electricity is produced by 440 nuclear reactors in 31 countries. The country that gets the highest percentage of its electricity from nuclear power is France. Its 59 reactors generate more than 78 percent of its electricity. Nuclear waste is the spent nuclear fuel from a reactor. The fuel is considered spent when the fission byproducts — the atoms left over from the splitting process — prevent free neutrons from splitting more uranium or plutonium. It takes three or four years to get to this point in the process. The waste is highly radioactive, so it must be stored in steel-lined concrete pools or in dry caskets. As of 2003, nuclear reactors in the United States had created about 49,000 tons of waste, according to the Department of Energy. Some countries, like Japan and France, reprocess their nuclear waste to extract the unspent uranium-235 and plutonium-239. This can be returned to use in nuclear power plants or used to create a nuclear bomb.

_

What are thorium-fueled reactors, and how are they different from uranium-fueled reactors?

Scientists are trying to perfect ways to use the element thorium to fuel reactors instead of uranium because it is three times more abundant in nature. It also leaves behind less nuclear waste, and that waste is harder to exploit for use in nuclear weapons. Thorium reactors produce less waste because, in a nuclear chain reaction, thorium atoms break down into fewer unusable atoms than does uranium. In addition, with the right design, thorium-fueled reactors generate 80 percent fewer plutonium-239 atoms — a key ingredient in atomic bombs. The reactors do produce another possible weapons material, uranium-233, but it is difficult to separate from the other, highly radioactive uranium isotopes that surround it. In fact, a thorium-fueled reactor could actually eat up existing stockpiles of plutonium by using it as a “seed” fuel. A seed is necessary because it’s harder to start a nuclear chain reaction with thorium than with uranium.

_

Why use nuclear power?

Unlike burning fossil fuels, using nuclear fission to generate electricity produces no soot or greenhouse gases. This helps keep the skies clean and doesn’t contribute to global warming. The World Nuclear Association estimates that the electricity industry would add 2.6 billion tons of carbon dioxide to the atmosphere each year if it used coal power instead of nuclear. Some governments also like nuclear power because it reduces their dependency on foreign oil. Finally, the fuel used to power nuclear reactors is very compact in comparison to fossil fuels. For instance, one pound of uranium can supply the same energy as 3 million pounds of coal. This makes it attractive for use in nuclear-powered vehicles like submarines, aircraft carriers and spacecraft.

_

Safety of nuclear power plant:

Nuclear power plants are some of the most sophisticated and complex energy systems ever designed. Any complex system, no matter how well it is designed and engineered, cannot be deemed failure-proof. The reactors themselves were enormously complex machines with an incalculable number of things that could go wrong. When that happened at Three Mile Island in 1979, another fault line in the nuclear world was exposed. One malfunction led to another, and then to a series of others, until the core of the reactor itself began to melt, and even the world’s most highly trained nuclear engineers did not know how to respond. The accident revealed serious deficiencies in a system that was meant to protect public health and safety. A fundamental issue related to complexity is that nuclear power systems have exceedingly long lifetimes. The timeframe involved from the start of construction of a commercial nuclear power station, through to the safe disposal of its last radioactive waste, may be 100 to 150 years. There are concerns that a combination of human and mechanical error at a nuclear facility could result in significant harm to people and the environment. Operating nuclear reactors contain large amounts of radioactive fission products which, if dispersed, can pose a direct radiation hazard, contaminate soil and vegetation, and be ingested by humans and animals. Human exposure at high enough levels can cause both short-term illness & death and longer-term death by cancer and other diseases. It is impossible for a commercial nuclear reactor to explode like a nuclear bomb since the fuel is never sufficiently enriched for this to occur. Nuclear reactors can fail in a variety of ways. Should the instability of the nuclear material generate unexpected behavior, it may result in an uncontrolled power excursion. Normally, the cooling system in a reactor is designed to be able to handle the excess heat this causes; however, should the reactor also experience a loss-of-coolant accident, then the fuel may melt or cause the vessel in which it is contained to overheat and melt. This event is called a nuclear meltdown. After shutting down, for some time the reactor still needs external energy to power its cooling systems. Normally this energy is provided by the power grid to which that plant is connected, or by emergency diesel generators. Failure to provide power for the cooling systems, as happened in Fukushima-Japan, can cause serious accidents. Nuclear reactors become preferred targets during military conflict and, over the past three decades, have been repeatedly attacked during military air strikes, occupations, invasions and campaigns. The most important barrier against the release of radioactivity in the event of an aircraft strike on a nuclear power plant is the containment building and its missile shield. Nuclear power plants are inherently robust structures that (various studies demonstrated) provide adequate protection in a hypothetical attack by an airplane. The nuclear industry, particularly in Japan, has felt a need to tell the public that nuclear power is safe in some absolute way. Many government agencies and nuclear companies have promoted a public myth of “absolute safety” that nuclear power proponents had nurtured over decades. The tsunami that began the Fukushima nuclear disaster could and should have been anticipated and in March 2012, Prime Minister Yoshihiko Noda acknowledged that the Japanese government shared the blame for the Fukushima disaster, saying that officials had been blinded to the country’s “technological infallibility”, and were all too steeped in a “safety myth”.

_

Electricity from water:

There are two primary methods for generating electricity from water. One method uses the energy potential of trapped water in dams in a more sophisticated version of the water wheel, and the other captures energy from ocean waves. Electricity generated from water is entirely renewable, since water is an abundant natural resource and no water is expended during the electricity generation process. For this reason, many nations rely heavily on hydroelectric power because they want to promote sustainable energy production.

_

Electricity generated from water on the ocean is known as wave power or wave energy. This method of power generation uses changes in the air levels of sealed chambers to power turbines. These chambers are floated on parts of the ocean with high wave activity, ensuring that a great deal of electric energy can be produced. Not all areas of the ocean are suitable for the generation of wave power, but some seaside communities have taken advantage of the technology to power themselves.

_

Hydroelectricity:

_


_

Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity consumption, and 3,427 terawatt-hours of electricity production in 2010. The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour. Hydro is also a flexible source of electricity since plants can be ramped up and down very quickly to adapt to changing energy demands. However, damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife. Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO2) than fossil fuel powered energy plants.

_

Hydropower is a process in which flowing water is used to spin a turbine connected to a generator. There are two basic types of hydroelectric systems that produce power. In the first system, flowing water accumulates in reservoirs created by the use of dams. The theory is to build a dam on a large river that has a large drop in elevation. The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carries electricity to your home and mine. Dam operators can determine the amount of energy produced by regulating the flow of water; most dams are capable of generating far more power than they do on a daily basis, which can be useful when there are problems at other power plants and facilities. The water continues past the propeller through the tailrace into the river past the dam. In the second system, called run-of-river, the force of the river current (rather than falling water) applies pressure to the turbine blades to produce power.

__

Geothermal power:

Geothermal power comes from heat energy buried beneath the surface of the earth. For every 100 meters you go below ground, the temperature of the rock increases about 3 degrees Celsius. Or for every 328 feet below ground, the temperature increases 5.4 degrees Fahrenheit. So, if you went about 10,000 feet below ground, the temperature of the rock would be hot enough to boil water. In some areas of the country, enough heat rises close to the surface of the earth to heat underground water into steam, which can be tapped for use at steam-turbine plants.

_

Solar power:

Solar power is derived from the energy of the sun. However, the sun’s energy is not available full-time and it is widely scattered. The processes used to produce power using the sun’s energy have historically been more expensive than using conventional fossil fuels. There are two main ways to collect solar energy. The first consists of solar heat conversion to electricity through the use of gases. Solar furnaces use large ground-based arrays of mirrors to direct all incoming light towards a centralized point where water is heated to boiling. The resulting steam powers turbine dynamos, which produce electrical power. Another solar thermal power generation methods is direct air heating, in which a glass greenhouse covering a large area of land absorbs sunlight to heat air. A central tower channels all heated air up past turbines, which power dynamos and make power. These types of plants can use radiative heating from the ground during evening hours. Both solar thermal methods produce no waste, but the power output is limited in comparison to nuclear power generation. The second method involves photovoltaic cells made from semiconductor materials. Photovoltaic conversion generates electric power directly from the light of the sun in a photovoltaic (solar) cell. Arrays of these cells capture and directly convert solar energy to electricity. This solar power generation technique also has no waste products, but the inefficiency and unreliability of the process makes its application limited. Less than 1% of the America’s generation is based on solar power.

_

The energy from the sun is captured through photovoltaic cells (solar panels) that are typically mounted on the side of your roof that has the most exposure to the sun (north or west). With a solar system, your home or business remains connected to the main electricity grid that powers your area, so:

1. Any electricity that your system generates above what you use is fed back into the grid.

2. When you require more electricity than you are producing, your system imports it from the grid automatically.

3. Your electricity bill is calculated as the difference between the amount of electricity you export from your solar system and the amount you import from the grid – you only pay for the electricity you use that is over and above what your solar energy system produces.

By using solar electric systems to power your home or business you are reducing greenhouse gas emissions and your electricity bills. A 1 kWh photovoltaic (solar electricity) system would prevent the mining of 150 pounds (60 kg) of coal, prevent 300 pounds (136 kg) of CO2 (as well as NO and SO2) from escaping into the environment, and save 105 gallons (397 liters) of water from consumption.

__

Wind power:

Wind power is derived from the conversion of the energy contained in wind into power. Wind power, like the sun, is rapidly growing source of power. A wind turbine is similar to a typical wind mill. Wind has been the fastest growing renewable electricity source worldwide, with an average annual growth rate of 24% over the period 1990-2005. Replacing one month’s use of fossil fuels with 100 kWhs of wind power is comparable to keeping your car off the road for 2,400 miles (3,862 km). In order for a wind turbine to work efficiently, wind speeds usually must be above 12 to 14 miles per hour. Wind has to be this speed to turn the turbines fast enough to generate electricity. The turbines usually produce about 50 to 300 kilowatts of electricity each.

_

Study finds bigger wind turbines produce greener electricity:

In a study that could solidify the trend toward construction of gigantic windmills, researchers from Switzerland and the Netherlands have concluded that the larger the wind turbine, the greener the electricity it produces. Their report appears in ACS’ journal Environmental Science & Technology.  Marloes Caduff and colleagues point out that wind power is an increasingly popular source of electricity. It provides almost 2% of global electricity worldwide, a figure expected to approach 10% by 2020. The size of the turbines also is increasing. One study shows that the average size of commercial turbines has grown 10-fold in the last 30 years, from diameters of 50 feet in 1980 to nearly 500 feet today. On the horizon are super-giant turbines approaching 1,000 feet in diameter. Advanced materials and designs permit the efficient construction of large turbine blades that harness more wind without proportional increases in their mass or the masses of the tower and the nacelle that houses the generator. That means more clean power without large increases in the amount of material needed for construction or fuel needed for transportation.

_

Biomass:

Biomass refers to wood, garbage, crops, harvest residues, agricultural waste, urban refuse, or methane gas produced by landfills that are burned to spin turbines and produce electricity. These sources replace fossil fuels in the boiler. The combustion of wood and waste creates steam that is typically used in conventional steam-electric plants. Biomass accounts for less than 1% of the power generated in the United States. Biomass is an attractive energy source because it avoids two drawbacks accompanying most other forms of renewable energy: high cost of collection and intermittency. The biomass collectors are the leaves of plants, requiring much less capital than wind turbines or PV cells and providing a convenient medium for energy storage, allowing electricity to produced on-demand, and contributing no net carbon dioxide to the atmosphere. However, if biomass were used for electricity production on a large scale, the impacts would be significant. For example, commercial applications of biomass would require vast acreage of fertile land to be committed to trees or crops grown specifically for energy production. Furthermore, biomass-fueled electricity production would also be extremely water intensive. Put in perspective, to produce electricity for just one household over the course of a year with biomass as a source would require over 25,000 gallons of water and almost three quarters of an acre of land. It also produces 232 pounds of carbon monoxide per household each year — more than thirty times the level of any other source, as well as significant amounts of other air pollutants. Waste is not considered a viable option for large-scale electricity production and is not a truly renewable resource.

_

Waste-to- Energy plant to generate electricity:

Waste-to-energy refers to any waste treatment that creates energy in the form of electricity or heat from a waste source that would have been disposed of in a landfill, otherwise known as municipal solid waste. Waste-to-energy is a renewable energy because its fuel source, garbage, is sustainable and is not depleted. According to the U.S. Environmental Protection Agency, waste-to-energy is a clean, reliable, renewable source of energy. Today, the U.S. burns 14 percent of its solid waste and there are 90 waste-to-energy plants in the United States. Waste-to-energy plants work a lot like coal-fired power plants. The difference is the fuel. Waste-to-energy plants use garbage, not coal, to fire an industrial boiler. The energy produced by the nation’s 90 waste-to-energy facilities is the electricity generating equivalent of 30 million barrels of crude oil. For every ton of trash disposed in a waste-to-energy plant, there is one ton less of carbon dioxide emission released into the air due to avoiding land disposal and fossil fuel generation. The energy produced by the America’s waste-to-energy plants is enough to meet the energy needs of 2.3 million American homes. America’s 90 waste-to-energy plants displace 7.8 million tons of coal that otherwise would be combusted for energy each year. Many are concerned that burning garbage may harm the environment. Waste-to-energy plants can produce air pollution when the fuel is burned to produce steam or electricity. The burning of the garbage releases the chemicals and substances found in the waste. These chemicals can be hazardous to people and the environment if they are not properly controlled. Another concern is that waste-to-energy plants will impede recycling programs. If all the waste is burned then there will be little incentive to recycle used products. However because of the nature of most waste recycling and waste-to-energy can actually complement each other.

_

Description of the biomass CHP technology based on a vegetable oil combustion engine:

Combustion engines convert the chemical energy of fuels into mechanical energy. The engine is attached to the shaft of the generator and provides the mechanical energy to drive the generator to produce electricity. Combustion engines have one or more cylinders in which fuel combustion occurs. Combustion engines can generate electricity almost immediately upon start-up. For this reason, internal combustion generators based on fossil fuels are often used to provide emergency power and as solutions for base-load or peak-load electricity supplies in remote or inaccessible areas throughout the world. During combustion, the pressure and temperature increase is very high and this allows high conversion efficiency for small units. Most engine systems for power generation use diesel oil or heavy fuel oil as liquid fuel. But the commitment to the continuous growth of renewable energy production is giving increasing room for the use of liquid biomass in combustion engines. Therefore researchers have developed solutions to burn liquid fuels such as crude vegetable oils (rape seed oil, olive oil and palm oil) and some waste and recycled biofuels (animal fat, waste cooking oil, recycled frying fat, etc) in combustion engines.

_

Land Requirements to generate electricity from various sources:

Table below shows land required each year for facilities that produce 1 billion kWh/yr of electricity (enough to supply a city of 100,000 people). Some sources of electricity (such as hydro) require a one-time land allotment and no new land is disrupted each year. Other sources (such as coal) have one-time land allotments in the construction of the power plant, but also require new land to be disrupted each year for fuel extraction

_

Source of electricity Hectares per billion kWh
Coal

363

Natural gas

                                                                                   9

Nuclear

48

Hydroelectric

75,000

Wind

                                                                           11666

Photovoltaics (solar)

1350 – 2700

Biomass

132,000 -220,000


It is clear that natural gas and nuclear power need least land.

_

Water footprint of electricity:

Although the water used for electricity is largely “out of sight and out of mind” for most people, the coal, nuclear and natural gas power plants that provide most of our electricity simply can’t function without it. Our power sector is built for a water-rich world. Conventional fossil-fuel and nuclear power plants require water to cool the steam they generate to make electricity. At some power plants, a lot of the water they withdraw gets evaporated in the cooling process; at others, much of the water is discharged back to its source (albeit hotter). The bottom line: Most power plants need a huge, steady supply of water to operate, and in hot dry summers, that water can become hard to secure. More water is used to cool these plants than is used for irrigation, lawn watering or any other use. And, alarmingly, their share of water use is increasing. This problem is only going to get worse if we build more coal, nuclear and natural gas plants. We’ll end up building more dams, draining more aquifers and sucking more rivers dry. In short, our water supplies and energy production are on a collision course with each other. Our current electrical grid (dominated by coal, nuclear and natural gas) uses approximately 40,000 gallons of water to produce a typical household’s monthly electricity needs. In 2005, power plants accounted for over 40 percent of all freshwater withdrawn in the U.S. According to researchers at the Virginia Water Resources Research Center, in Blacksburg, Va., fossil-fuel-fired thermoelectric power plants consume more than 500 billion L of fresh water per day in the United States alone. That translates to an average of 95 L of water to produce 1 kilowatt-hour of electricity. Water plays a number of roles in energy production, including pumping crude oil out of the ground, helping to remove pollutants from power plant exhaust, generating steam that turns turbines, flushing away residue after fossil fuels are burned, and keeping power plants cool.

_

What the Virginia Water Resources group found is both heartening and distressing. Natural gas, the fuel of choice for most of the ultraefficient electricity-generating turbines being built to meet the world’s growing energy demands, yields the most energy per unit volume of water consumed. Fewer than 38 L of water are required to extract enough natural gas to generate 1000 kWh of electricity. By the time a coal-fired power plant has delivered that much energy, roughly 530 L of water has been consumed.

_


_

The big shocker is that biodiesel doesn’t look so ”green” when considered in the context of water consumption. More than 180 000 L of water would be needed to produce enough soybean-based biodiesel to power a home for one month. It takes a lot of water to irrigate the soil in which the soybeans grow, and even more is used in turning the legumes into fuel.

_

The researchers also looked at water consumption by type of electricity generation:


_

The water footprint of electricity from hydropower:

Hydropower accounts for about 16% of the world’s electricity supply. Although dams often have big environmental and social impacts, proponents of hydropower regard it as a comparatively clean, low-cost and renewable form of energy. It has been debated whether hydroelectric generation is merely an in-stream water user or whether it also consumes water, in the sense of effectively taking away water from the river. A study assessed the blue water footprint of hydroelectricity – the water evaporated from manmade reservoirs to produce electric energy – for 35 selected sites. The aggregated blue water footprint of the selected hydropower plants is 90 Gm3/yr, which is equivalent to 10% of the blue water footprint of global crop production in the year 2000. The total blue water footprint of hydroelectric generation in the world must be considerably larger if one considers the fact that this study covers only 8% of the global installed hydroelectric capacity. Hydroelectric generation is thus a significant water consumer. The average water footprint of the selected hydropower plants is 68 m3/GJ. Great differences in water footprint among hydropower plants exist, due to differences in climate in the places where the plants are situated, but more importantly as a result of large differences in the area flooded per unit of installed hydroelectric capacity.

_

Massive Drought May Hinder Electricity Generation:

Power plants can be divided into gulpers and sippers of water.  Nuclear and coal power plants, in particular, use enormous quantities of water for cooling purposes, and the drought may hinder operations, if it persists much longer. Hydro production, of course, falls significantly during droughts, while wind and solar PV do not consume water at all. As the drought continues and the heat smashes records, another fact to watch is the temperature of water used by power plants to cool. Some power plants cannot use water that becomes too warm and have curtailed operations in the USA, France, and elsewhere as a result. When air-conditioning is maxed during the hottest 100 hours of the year, every possible power plant and demand response resource can be needed to keep air conditioners and lights running. Grid systems are stressed. And during those peak demand hours, the loss of any generation for any reason endangers reliability. The drought reminds that the water needs of the various power generation types can be an important factor in determining what plants are best operationally, economically, and environmentally.  In some locations, the supply of water and cool-enough water are as important as capital costs and fuel costs in judging what to build in the future.

_

Water Requirements:

Table below shows water consumption for fuel extraction, and the construction and operation of electricity-generating facilities in terms of acre-feet of water used per GWh of power produced. Data includes consumptive water use only (most of which is lost as evaporation from cooling systems) and does not include non-consumptive water use (which returned to the water body from which it was drawn), unless otherwise indicated.

_

Source of electricity Acre-ft water per GWh
Coal

1.5 – 3.1

Natural gas

0.8

Nuclear

2.6 – 4.1

Hydroelectric

66,000

Wind

~0

Photovoltaics

0.1

Biomass

8.4

Natural gas, wind power and solar system use least water than rest of electricity sources.

_

Environmental pollution due to electricity generation:

The production of electricity causes more damage to the environment than any other single human activity. Most scientists agree that emissions of pollutants and greenhouse gases from fossil fuel-based electricity generation account for a significant portion of world greenhouse gas emissions; in the United States, electricity generation accounts for nearly 40 percent of emissions of CO2 amounting to 2,166 million metric tons, the largest of any source. Transportation emissions are close behind, contributing about one-third of U.S. production of carbon dioxide. In the United States, fossil fuel combustion for electric power generation is responsible for 65% of all emissions of sulfur dioxide, the main component of acid rain. Electricity generation is the fourth highest combined source of NO2, carbon monoxide, and particulate matter in the US. It is responsible for millions of miles of rivers and streams being disrupted by dams, hundreds of tons of nuclear waste that must find a permanent home somewhere, and thousands of tons of air pollutants that are a major cause of respiratory problems. In July 2011, the UK parliament tabled a motion that “levels of (carbon) emissions from nuclear power were approximately three times lower per kilowatt hour than those of solar, four times lower than clean coal and 36 times lower than conventional coal”. Though PV generation is positioned as environmentally friendly, fabrication of PV cells utilizes substantial amounts of water in addition to toxic chemicals such as phosphorus and arsenic. These are often overlooked when promoting PV. Because of strict environmental regulations in the United States, for example, PV fabrication is often performed in countries with lower standards, such as China.

_

Electricity accounts for 40% of global energy-related CO2 emissions as combustion of fossil fuel is a major source of electricity; these emissions will grow by 58% globally by 2030. Carbon dioxide contributes at least 60% of the human-induced increase in the greenhouse effect. Electricity generation is one of the major sources of this carbon dioxide, giving rise to about 9.5 billion tons per year – 40% of it, or about one quarter of the human-induced greenhouse increase. Coal-fired electricity generation gives rise to nearly twice as much carbon dioxide as natural gas per unit of power, but hydro and nuclear do not directly contribute any. If the amount of nuclear power were doubled, emissions from electricity generation would drop by one quarter.

_

Natural gas creates significantly smaller environmental impacts than coal. On a Btu basis, natural gas combustion generates about half as much carbon dioxide, or CO2, as coal, less particulate matter, and very little sulfur dioxide or toxic air emissions. Natural gas combustion may, however, produce nitrogen oxides and carbon monoxide in quantities comparable to coal burning. Ongoing use of natural gas inevitably results in methane emissions, a very potent greenhouse gas contributing to global climate change. Natural gas drilling and exploration can negatively impact wilderness habitat, wildlife and public open space. Among the list of potential negative land impacts associated with natural gas are erosion, loss of soil productivity, increased runoffs, landslides and flooding. If natural gas is compared to coal combustion, CO2 emissions are significantly reduced, but natural gas combustion still results in a net increase in CO2 emissions and therefore can contribute to climate change.

_

Burning oil for electricity pollutes the air, water and land but some of the worst environmental woes associated with oil are linked to drilling, transporting and refining.  Burning oil to generate electricity produces significant air pollution in the forms of nitrogen oxides, and, depending on the sulfur content of the oil, sulfur dioxide and particulates. Carbon dioxide and methane (as well as other greenhouse gases), heavy metals such as mercury, and volatile organic compounds (which contribute to ground-level ozone) all can come out of the smoke stack of an oil-burning power plant. The operation of oil-fired power plants also impacts water, land use and solid waste disposal. Similar to the operations of other conventional steam technologies, oil-fired conventional steam plants require large amounts of water for steam and cooling, and can negatively impact local water resources and aquatic habitats. Sludges and oil residues that are not consumed during combustion became a solid waste burden and contain toxic and hazardous wastes. Drilling also produces a long list of air pollutants, toxic and hazardous materials, and emissions of hydrogen sulfide, a highly flammable and toxic gas. All of these emissions can impact the health and safety of workers and wildlife. Loss of huge stretches of wildlife habitat also occurs during drilling. Refineries, too, spew pollution into the air, water and land (in the form of hazardous wastes). Oil transportation accidents can result in catastrophic damage killing thousands of fish, birds, other wildlife, plants and soil.

_

The need for developing alternative energy to counter the increasingly devastated state of the world’s environment is the priority. Using fossil fuels (gas, coal, and oil) produce a great deal of pollution and toxic waste products which pollute the earth’s biosphere. Oil, coal and natural gas produce toxic smoke that sends pollutants into the air and causes global warming. The melting ice in the North and South Poles can speed-up global warming because the Arctic ice protects Earth’s from absorbing 100 per cent of the sun’s intense heat. The sun is the Earth’s main source of energy, but without protection, the planet would not be able to sustain life. Clouds, like ice, help to reflect 30 per cent of the sun’s rays, which keeps the planet at the right temperature while the remaining 70 per cent warms the Earth. But, greenhouse gas emissions act like an invisible wrapper that traps the sun’s heat and causes the planet to warm up. This increased heat melts the north and south ice caps thus taking away some of Earth’s protection from the sun thus causing wildfires, heat waves, flooding, droughts and much worse – all because of global warming. In fact, studies conducted from satellite images show that the polar ice cap in the Arctic is melting at least nine percent every ten years, which means by the end of the 21st century, there could be no more summer ice in the Arctic.

__

Air Pollution Emissions:

Table below shows emissions of 5 major air pollutants from electric power generation over the fuel lifecycle. Tr stands for trace (less than 0.01 tons/GWh). Particulates are abbreviated as TSP (total suspended particulates).

_

Tons of pollutants per GWh
Source of electricity

SO2

NO2

TSP

CO

VOCs

Coal

2.97

2.99

1.63

0.30

0.10

Natural gas

0.37

0.25

1.18

tr

tr

Nuclear

0.03

0.03

tr

0.02

tr

Hydroelectricity

tr

tr

tr

tr

tr

Wind

tr

tr

tr

tr

tr

Photovoltaics

0.02

0.01

0.02

tr

tr

Biomass

0.15

0.61

0.51

11.36

0.77

It is clear that coal is least environment friendly.

_

Carbon Dioxide Emissions:

Table below shows carbon dioxide emissions per GWh of electricity produced over the total fuel cycle. A typical person uses about a tenth of a GWh of electricity in a year.

_

Source of electricity

Tons of CO2/GWh

Coal

751 – 964

Natural gas

484 – 590

Nuclear

7.8

Hydroelectric

3.1 – 10.0

Wind

7.4

Photovoltaics

5.4

Biomass

see footnote

Biomass: If forests were harvested sustainably, the use of biomass for electricity would yield no net CO2 increase in the atmosphere because the amount of carbon emitted during combustion equals the amount that would be removed from the atmosphere during regrowth. However, if energy crops were grown using industrial agricultural methods, the CO2 emitted per unit of electricity produced may be significantly greater than zero due to the energy required for fertilizers, pesticides, and planting and harvesting.

_

Every $1 of electricity from coal does $2 in damage to U.S.:

According to the prestigious American Economic Review, harm from coal-fired electrical plants costs more than twice as much as the electricity they generate. All told, coal plants cause $53 billion in damage every year. And none of that even takes climate impacts into account. Health effects from coal-fired plants — increased deaths from sulfur dioxide, nitrogen oxides, and particulates — comprise more than a quarter of pollution-related damages from U.S. industry. That’s a conservative estimate, done by centrist economists, that leaves out the health effects of climate change altogether. But probably more important is the conclusion that coal plants are a cost-benefit nightmare. The findings show that, contrary to current political mythology, coal is underregulated. On average, the harm produced by burning the coal is over twice as high as the market price of the electricity. In other words, some of the electricity production would flunk a cost-benefit analysis. If I extrapolate damage due to coal mining & combustion to generate electricity worldwide from the above study, the potential or presumed damage caused by nuclear power plant appear miniscule. This is a key reason not to ignore nuclear fission. So called intellectuals who hate nuclear power to generate electricity ought to change their mind. Uniquely (at present), it is a proven fit-for-service low-carbon “plug-in” alternative for coal that is commercially available, deployed widely in some countries (e.g., France, U.S., South Korea), is highly scalable, and its engineering and operational experience have advanced greatly over the last 50 years. It indisputably has its own problems, but so do all of our other electricity options. Indeed, I would argue that the principal limitations on nuclear fission are not technical, economic or fuel-related, but are instead linked to complex issues of societal acceptance, fiscal and political inertia, and inadequate critical evaluation of the real-world constraints facing low-carbon alternatives.

_

Alternative Energy v/s Renewable Energy:

There is a marked difference between the terms “alternative energy” and “renewable energy”. Alternative energy refers to any form of energy which is an alternative to the traditional fossil fuels, like oil, natural gas and coal. Renewable energy, on the other hand, refers to forms of alternative energy that are renewed by the natural processes of the Earth, such as solar energy or wind energy.

_


_

Renewable and nonrenewable energy sources can be used to produce secondary energy sources including electricity and hydrogen.  Renewable energy sources include solar energy, which comes from the sun and can be turned into electricity and heat. Wind, geothermal energy from inside the earth, biomass from plants, and hydropower and ocean energy from water are also renewable energy sources. However, we get most of our energy from nonrenewable energy sources, which include the fossil fuels (oil, natural gas, and coal) and nuclear fission.

_

New research from the Helsinki University of Technology’s Advanced Energy Systems in Espoo, Finland, shows that with the help from global cooperation and investment renewable energy will “exceed all previous estimates.”According to the new findings renewable energy technologies like wind and photovoltaics could supply 40% of the world’s electricity by 2050. But this could only become a reality if the renewable technology is backed up by adequate financial and political support. If not, the renewable share is likely to hover somewhere below 15 percent.

_

What is green energy?

Green energy is electricity derived from renewable or clean resources such as hydro energy, wind energy, solar energy, geothermal energy and biofuels. Nuclear power plants do not emit carbon dioxide, and therefore may be considered to be a green energy source. Green energy plans work by providing electricity from renewable or clean sources to the National Grid, which will then be used to power your home.

_

The cost of power generation varies by fuel type. The table below shows comparison of cost of power generated by various sources.


The cheapest is nuclear and costliest is solar from above table. Natural gas is better alternative considering less capital and moderate total cost.

__

How much coal, natural gas, or petroleum is used to generate a kilowatt-hour (KWh) of electricity?

Amount of fuel used to generate one kilowatt-hour (KWh):

1. Coal = 0.00052 Short Tons or 1.03 Pounds

2. Natural Gas = 0.01003 Mcf (10 cubic feet)

3. Residual Fuel Oil = 0.0016 Barrels

_

KWh generated per unit of fuel used:

A) 1,942 kWh per Ton of Coal or 0.97 kWh per Pound of Coal

B) 100 KWh per Mcf (1000 cubic feet) of Natural Gas

C) 610 KWh per Barrel of Residual Fuel Oil, or 14.5 KWh per Gallon

_

Pros and cons of electricity sources:

Source Advantages Disadvantages
Wind   Renewable energy source  Very low greenhouse gas emissions  Very low air pollution emissions  Very low water requirements  Very safe for workers and public   Intermittent energy source  Limited to windy areas  Potentially high hazard to birds  Moderate land requirements
Solar   Renewable energy source  Very low greenhouse gas emissions  Very low air pollution emissions  Very low water requirements  Modular, low-profile, low-maintenance  Very safe for workers and public   Intermittent energy source  High land requirements  Expensive  Manufacture involves some toxics
Biomass   Renewable energy source  Very low greenhouse gas emissions  Can produce energy on-demand  Energy is easily stored   Low energy return on investment  High air pollution emissions  Very high water and land requirements  High occupational hazards
Small Hydro   Renewable (if silt removed in reservoir)  Very low greenhouse gas emissions  Very low air pollution emissions  Inexpensive to build and operate  Safe for workers and public   Dependent on stream flow  Large numbers of small dams can have significant effects on terrestrial and aquatic habitats, possibly as great as a large dam producing the same amount of electricity
Large Hydro   Very high return on energy investment  Very low greenhouse gas emissions  Very low air pollution emissions  Inexpensive once dam is built  Can produce energy on-demand  Provide water storage and flood-control   Non-renewable (silt removal unfeasible)  Very high land requirements  Extremely high impacts to land and water habitat  Best sites are already developed or off-limits  Disastrous impacts in case of dam failure
Natural Gas   Inexpensive  Low land requirements  Can produce energy on-demand  Relatively safe for workers and public   Non-renewable energy source  High greenhouse gas emissions  Relatively moderate air pollution emissions  Danger of explosion if handled improperly
Coal   Inexpensive  Abundant  Low land requirements  Can produce energy on-demand   Non-renewable energy source  Very high greenhouse gas emissions  Very high air pollution emissions  High land/water impacts from acid rain, mine drainage  Highly hazardous occupation
Nuclear   Low greenhouse gas emissions  Low air pollution emissions  Low land requirements for power plants (though not for waste storage)  Can produce energy on-demand   Non-renewable energy source  High water requirements  Relatively expensive  Waste remains dangerous for thousands of years  Serious accident would be disastrous

_

Rating the electricity sources:

Wind

Solar

Small Hydro

Large Hydro

Nat. Gas

Biomass

Coal

Nuclear

Renewability

10

10

9

7

1

8

1

1

Land

8

7

3

2

8

1

1

1

Water

10

10

2

1

7

2

1

1

Air and Climate

10

10

10

10

2

6

1

7

Health and Safety

10

10

9

7

5

6

2

1

Energy Return Ratio

7

8

10

10

8

1

7

2

Price

8

2

9

9

7

4

6

1

Overall

9.0

8.1

7.4

6.6

5.4

4.0

2.7

2.0

Obviously, wind and solar are best sources of electricity but today, less than 3 % of total electricity generated worldwide comes from these noble sources.

_

Electricity storage:

Electric charge can be stored in chemical form in electric cells (which can be strung together to form batteries of two or more cells) and used at a later time. Some of these cells are rechargeable by driving the electrons in the opposite direction. Charges can also be stored in capacitors which are essentially pairs of conducting planes separated by an insulating material such as plastic, glass, mica, or even air. The unit of capacitance is the farad which is that capacitance that will allow one volt of EMF to store one coulomb of charge. In actual practice capacitors are generally in the microfarad and picofarad ranges.

_

Battery:

Inside the battery, a reaction between the chemicals takes place. But reaction takes place only if there is a flow of electrons. Batteries can be stored for a long time and still work because the chemical process doesn’t start until the electrons flow from the negative to the positive terminals through a circuit. A very simple modern battery is the zinc-carbon battery. This battery contains acidic material within and a rod of zinc down the center. When zinc is inserted into an acid, the acid begins to eat away at the zinc, releasing hydrogen gas and heat energy. The acid molecules break up into its components: usually hydrogen and other atoms. The process releases electrons from the Zinc atoms that combine with hydrogen ions in the acid to create the hydrogen gas. If a rod of carbon is inserted into the acid, the acid does nothing to it. But if you connect the carbon rod to the zinc rod with a wire, creating a circuit, electrons will begin to flow through the wire and combine with hydrogen on the carbon rod. This still releases a little bit of hydrogen gas but it makes less heat. Some of that heat energy is the energy that is flowing through the circuit. The energy in that circuit can now light a light bulb in a flashlight or turn a small motor. Depending on the size of the battery, it can even start an automobile. Eventually, the zinc rod is completely dissolved by the acid in the battery, and the battery can no longer be used. A battery produces electricity using two different metals in a chemical solution. A chemical reaction between the metals and the chemicals frees more electrons in one metal than in the other. Batteries are chemically-powered charge pumps. They contain “fuel” in the form of chemicals. When the chemical fuel becomes exhausted, the battery has “gone dead”. No chemicals ever leave the battery, so what happens to the fuel? It turns into waste products. If you have a rechargeable battery, then you can “recycle” the waste products. By pumping charges backwards through the battery, you force the chemical waste to turn back into fuel. This is a bit like pumping some exhaust into your car engine, and having gasoline come out the other end! The chemical reactions inside of rechargeable batteries are reversible, while the burning of gasoline is not.

_

Why permanent magnet does not function like battery?

Permanent magnets generate their magnetic field through two main mechanisms – firstly there is the orbital motion of electrons around the nucleus. Since the electrons are charged, this is equivalent to an electric current and sets up a magnetic field. Secondly, there is the spin of the electrons themselves – this again creates a magnetic field (although it is tempting to think of the electron as a little spinning charged object of finite size, this would be incorrect, the proper description being a quantum mechanical one). The net effect is that the atoms behave as tiny magnets. In ferromagnetic materials the motion has the right “collective” properties such that the atoms, which behave like a tiny magnets, are able to align their magnet’s directions (in local units called magnetic domains) to provide a large magnetic field. However (1) the orbital motion of the electric charge in the atoms is cyclical, and (2) the spin of the electron doesn’t move the charge from one place to another whereas what you’d need for a battery is a movement of charge which results in separation of positive and negative charge, to make available at the terminals. Thus permanent magnets can’t function as batteries.

_

Electric grid:

_


_

An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of three main components: 1) power stations that produce electricity from combustible fuels (coal, natural gas, biomass) or non-combustible fuels (wind, solar, nuclear, hydro power); 2) transmission lines that carry electricity from power plants to demand centers; and 3) transformers that reduce voltage so distribution lines carry power for final delivery.

_

AC power transmission:

Transmitting electricity at high voltage reduces the fraction of energy lost to resistance, which averages around 7%. For a given amount of power, a higher voltage reduces the current and thus the resistive losses in the conductor. For example, raising the voltage by a factor of 10 reduces the current by a corresponding factor of 10 and therefore the I2R losses by a factor of 100, provided the same sized conductors are used in both cases. Even if the conductor size (cross-sectional area) is reduced 10-fold to match the lower current the I2R losses are still reduced 10-fold. Long distance transmission is typically done with overhead lines at voltages of 115 to 1,200 kV. At extremely high voltages, more than 2,000 kV between conductor and ground, corona discharge losses are so large that they can offset the lower resistance loss in the line conductors. Measures to reduce corona losses include conductors having large diameter; often hollow to save weight, or bundles of two or more conductors.

_

High-voltage direct current (HVDC) is used to transmit large amounts of power over long distances or for interconnections between asynchronous grids. When electrical energy is required to be transmitted over very long distances, it is more economical to transmit using direct current instead of alternating current. For a long transmission line, the lower losses and reduced construction cost of a DC line can offset the additional cost of converter stations at each end. Also, at high AC voltages, significant (although economically acceptable) amounts of energy are lost due to corona discharge at the capacitance between phases or, in the case of buried cables, between phases and the soil or water in which the cable is buried. HVDC is also used for long submarine cables because over about 30 km length AC can no longer be applied. In that case special high voltage cables for DC are built. Many submarine cable connections – up to 600 km length – are in use nowadays. HVDC links are sometimes used to stabilize against control problems with the AC electricity flow. The power transmitted by an AC line increases as the phase angle between source end voltage and destination ends increases, but too great a phase angle will allow the generators at either end of the line to fall out of step. Since the power flow in a DC link is controlled independently of the phases of the AC networks at either end of the link, this stability limit does not apply to a DC line, and it can transfer its full thermal rating. A DC link stabilizes the AC grids at either end, since power flow and phase angle can be controlled independently.

_

Superconducting cables:

At very low temperatures – between -320 degrees F (-196 C) and -460 degrees F (-273 C) — certain metal and ceramic materials conduct electricity with virtually no resistance. Wires made of these superconducting materials can transmit 100-150 times more electricity than traditional copper wires without any losses in efficiency. (Wires that operate in the -320 degree F range are called “high-temperature” superconductors or HTS). You can still have losses if you use alternating current, but in DC applications, there is no loss at all.

_

High-temperature superconductors promise to revolutionize power distribution by providing lossless transmission of electrical power. The development of superconductors with transition temperatures higher than the boiling point of liquid nitrogen has made the concept of superconducting power lines commercially feasible, at least for high-load applications. It has been estimated that the waste would be halved using this method, since the necessary refrigeration equipment would consume about half the power saved by the elimination of the majority of resistive losses. Some companies such as Consolidated Edison and American Superconductor have already begun commercial production of such systems. In one hypothetical future system called a SuperGrid, the cost of cooling would be eliminated by coupling the transmission line with a liquid hydrogen pipeline. Superconducting cables are particularly suited to high load density areas such as the business district of large cities, where purchase of an easement for cables would be very costly.

_

Single wire earth return:

Single-wire earth return (SWER) or single wire ground return is a single-wire transmission line for supplying single-phase electrical power for an electrical grid to remote areas at low cost. It is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps, and light rail. Single wire earth return is also used for HVDC over submarine power cables.

_

Wireless power transmission:

Both Nikola Tesla and Hidetsugu Yagi attempted to devise systems for large scale wireless power transmission, with no commercial success. The photoelectric effect is more pervasive than most believe. It is one of the fundamental processes behind living systems. Tesla proved that electrical power can be wirelessly transmitted. The simple idea of the crystal radio may be far more profound than we think with major ramifications for the redesign of the power grid and power dependencies. The invention of the fractal antenna is something of an unannounced miracle of technology and is capable of receiving (and transmitting) a wide range of frequencies in a compact space. They are at the heart of all modern cell phones. This fractal antenna accumulator is based directly on the patents of Nikola Tesla. Tesla found that an antenna could collect energy and turn it into electron flow, which is the foundation of modern electronics. The accumulator uses diodes to exploit both phases of incoming electromagnetic radiation to charge two sets of batteries that are connected to a load. The load could easily be an inverter to generate AC electricity. In November 2009, LaserMotive won the NASA 2009 Power Beaming Challenge by powering a cable climber 1 km vertically using a ground-based laser transmitter. The system produced up to 1 kW of power at the receiver end. In August 2010, NASA contracted with private companies to pursue the design of laser power beaming systems to power low earth orbit satellites and to launch rockets using laser power beams. Wireless power transmission has been studied for transmission of power from solar power satellites to the earth. A high power array of microwave or laser transmitters would beam power to a rectenna. A rectenna is a rectifying antenna, a special type of antenna that is used to convert microwave energy into direct current electricity. They are used in wireless power transmission systems that transmit power by radio waves. A simple rectenna element consists of a dipole antenna with a diode connected across the dipole elements. The diode rectifies the AC current induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode. Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching. Large rectennas consist of an array of many such dipole elements. Major engineering and economic challenges face any solar power satellite project.

__

Efficiency of electricity:

The efficiency of electricity in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed (a fractional expression).

Electrical Efficiency = Power output / Power input X100 = % Efficiency

For instance, 746 watts is equivalent to one horsepower. If an electric motor were 100% efficient, a 1HP motor would only draw 746 watts of electricity. Look in any motor catalog, and you will see that typical 1HP motors draw around 1100 watts. So: (746 / 1100) X100 = 67.8%

The example motor has a 68% electrical efficiency. You can apply the same formula to any electrical device – heaters, amplifiers, transformers, etc.

_

For example, electrical efficiency of light bulbs is as follows:

Incandescent light bulb (normal light bulb): about 2 to 3%.

Compact fluorescent lamp (CFL): about 9% to 11%.

White light-emitting diode (LED) about 4%-18%

_

Efficiency of electricity generation:

The production of electricity in 2008 was 20,261 TWh, which was 11% of the solar energy the earth receives in one hour (174,000TWh). Sources of electricity were fossil fuels 67%, renewable energy 18%, and nuclear power 16%. The majority of fossil fuel usage for the generation of electricity was of coal and gas. Oil was only 7%. Ninety-two percent of renewable energy was hydroelectric followed by wind at 6% and geothermal at 1.8%. Solar photovoltaic was 0.06%, and solar thermal was 0.004%. Total energy consumed at all power plants for the generation of electricity was 4,398,768 ktoe (kilo ton of oil equivalent) which was 36% of the total for primary energy sources (TPES) of 2008. Electricity output (gross) was 1,735,579 ktoe (20,185 TWh), efficiency was 39%, and the balance of 61% was generated heat. A small part(145,141 ktoe, which was 3% of the input total) of the heat was utilized at co-generation heat and power plants. The in-house consumption of electricity and power transmission losses were 289,681 ktoe. The amount supplied to the final consumer was 1,445,285 ktoe (16,430 TWh) which was 33% of the total energy consumed at power plants and heat and power co-generation (CHP) plants.

_


_

66% of energy is lost as heat out of total energy consumed during electricity generation and 10% of energy is lost in electricity transmission in developed nations (far more in India: 40 % loss in transmission & theft).


Thermoelectrics can help retrieve lost heat energy into electrical energy.

_

Grid energy storage to regenerate electricity:


_

Demand for electricity from the world’s various grids varies over the course of the day and from season to season. For the most part, variation in electric demand is met by varying the amount of electrical energy supplied from primary sources. Increasingly, however, operators are storing lower-cost energy produced at night, then releasing it to the grid during the peak periods of the day when it is more valuable. Grid energy storage (also called large-scale energy storage) refers to the methods used to store electricity on a large scale within an electrical power grid. Electrical energy is stored during times when production (from power plants) exceeds consumption and the stores are used at times when consumption exceeds production. In this way, electricity production need not be drastically scaled up and down to meet momentary consumption – instead, production is maintained at a more constant level. This has the advantage that fuel-based power plants (i.e. coal, oil, gas) can be more efficiently and easily operated at constant production levels. An alternate approach to grid energy storage is the smart grid. The current power grid is designed to have generation sources respond on-demand to user needs, while a smart grid can be designed so that usage varies on-demand with production availability from intermittent power sources such as wind and solar. End-user loads can be actively shed by the utility during peak usage periods, or the cost per kilowatt can dynamically vary between peak and non-peak periods to encourage turning off non-essential high power loads.  Companies are researching the possible use of Electric Vehicles for meeting peak demand. A parked and plugged-in EV could sell the electricity from the battery during peak loads and charge either during night (at home) or during off-peak. Another grid energy storage method is to use off-peak or renewably generated electricity to compress air, which is usually stored in an old mine or some other kind of geological feature. When electricity demand is high, the compressed air is heated with a small amount of natural gas and then goes through turboexpanders to generate electricity.

_

Batteries:

Battery systems connected to large solid-state converters have been used to stabilize power distribution networks. For example in Puerto Rico a system with a capacity of 20 megawatts for 15 minutes is used to stabilize the frequency of electric power produced on the island. A 27 megawatt 15 minute nickel-cadmium battery bank was installed at Fairbanks Alaska in 2003 to stabilize voltage at the end of a long transmission line. Many “off-the-grid” domestic systems rely on battery storage, but storing large amounts of electricity in batteries or by other electrical means has not yet been put to general use. Batteries are generally expensive, have high maintenance, and have limited life spans, mainly due to pure chemical crystals that form inside the cells during the charge and discharge cycles. These crystals usually cannot be re-dissolved back into the electrolyte. They can grow large enough to apply significant mechanical pressure to interior structures inside the battery to bend plates, bulge battery casings, and short out individual cells. One possible technology for large-scale storage are large-scale flow batteries and liquid metal batteries. Another available way to store electric energy in batteries is to use lithium iron phosphate (LiFePO4) battery. They can be used for different purposes. Available power per unit changes between 100kWh up to 2MWh. Units could be connected in parallel, so there is no upper limit for capacity.

_

Flywheel:

Mechanical inertia is the basis of this storage method. A heavy rotating disc is accelerated by an electric motor, which acts as a generator on reversal, slowing down the disc and producing electricity. Electricity is stored as the kinetic energy of the disc.

_

Hydrogen:

Hydrogen is also being developed as an electrical energy storage medium. Hydrogen is produced, then compressed or liquefied, stored, and then converted back to electrical energy or heat. Hydrogen can be used as a fuel for portable (vehicles) or stationary energy generation. Compared to pumped water storage and batteries, hydrogen has the advantage that it is a high energy density fuel. Hydrogen can be produced either by reforming natural gas with steam or by the electrolysis of water into hydrogen and oxygen. Reforming natural gas produces carbon dioxide as a by-product. High temperature electrolysis and high pressure electrolysis are two techniques by which the efficiency of hydrogen production may able to be increased. Hydrogen is then be converted back to electricity in an internal combustion engine, or a fuel cell which convert chemical energy into electricity without combustion, similar to the way the human body burns fuel. The AC-to-AC efficiency of hydrogen storage has been shown to be in order of 40%, rendering hydrogen storage unsuitable for anything but special (mobile) applications. The main drawback is the high number of energy conversions required, compared to other storage techniques. In effect, a hydrogen storage businessman would have to sell the energy he bought for four times the buy price. The equipment necessary for hydrogen energy storage includes an electrolysis plant, hydrogen compressors or liquifiers, and storage tanks.

_

Pumped water:

In 2008 world pumped storage generating capacity was 104 GW, while other sources claim 127 GW, which comprises the vast majority of all types of grid electric storage – all other types combined are some hundreds of MW. In many places, pumped storage hydroelectricity is used to even out the daily generating load, by pumping water to a high storage reservoir during off-peak hours and weekends, using the excess base-load capacity from coal or nuclear sources. During peak hours, this water can be used for hydroelectric generation, often as a high value rapid-response reserve to cover transient peaks in demand. Pumped storage recovers about 75% of the energy consumed, and is currently the most cost effective form of mass power storage. The chief problem with pumped storage is that it usually requires two nearby reservoirs at considerably different heights, and often requires considerable capital expenditure. A new concept in pumped-storage is utilizing wind energy or solar power to pump water. Wind turbines or solar cells that direct drive water pumps for an energy storing wind or solar dam can make this a more efficient process but are limited. Such systems can only increase kinetic water volume during windy and daylight periods.

_

Superconducting magnetic energy:

Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature. A typical SMES system includes three parts: superconducting coil, power conditioning system and cryogenically cooled refrigerator. Once the superconducting coil is charged, the current will not decay and the magnetic energy can be stored indefinitely. In an SMES system, because the electrical current has zero resistance, the magnetic field once created will almost never be weakened unless the system breaks itself. So, compared to other systems, it loses the least amount of energy during storage making them very efficient. The stored energy can be released back to the network by discharging the coil. The power conditioning system uses an inverter/rectifier to transform alternating current (AC) power to direct current or convert DC back to AC power. The inverter/rectifier accounts for about 2–3% energy loss in each direction. SMES loses the least amount of electricity in the energy storage process compared to other methods of storing energy. SMES systems are highly efficient; the round-trip efficiency is greater than 95%. The high cost of superconductors is the primary limitation for commercial use of this energy storage method.

_

Electricity consumption:

Consumption of electric energy is measured by W·h (Watt x Hour).

1 W·h = 3600 joule = 859.8 calorie

One 100 watt light bulbs consume 876,000 W·h (876 kW·h) of energy in one year.

_

1000 watt-hour (Wh) = 1 kilowatt-hour (kWh)

1000 kWh = 1 megawatt-hour and so on as depicted in table below:

_

103 kW·h kilowatt hour
106 MW·h megawatt hour
109 GW·h gigawatt hour
1012 TW·h terawatt hour
1015 PW·h petawatt hour

_

Electric power per capita [in watt] = Total population electricity consumption [in MW·h/yr] · 1,000,000/ (365.25 x 24)/population.

Electric power per capita [in watt] = Total population electricity consumption [in MW·h/yr ] · 114.077116 /population.

1 MW·h/yr = 1,000,000 Wh/ (365.25 x 24) h = 114.077116 Watt

_

Currently, the world’s population consumes 15 terawatts of power from a combination of these energy sources. Just how much power is 15 terawatts? Let’s think of it in smaller and more familiar terms: watts. Many of the lightbulbs in our homes consume 100 watts of energy. One terawatt could power about 10 billion 100-watt lightbulbs at the same time.

_

The graph below shows electricity consumption in KWHr per capita worldwise.


_

According to the International Energy Outlook 2005, released by the Energy Information Administration (EIA), the worldwide consumption of electricity is expected to increase gradually. Much of the growth in energy use is projected for the developing world. However, much more attention should be devoted to India and China as the economy of both regions grows rapidly, followed by the increase of the consumption of electricity.

_


_

The figure above shows World Electricity Consumption Highlights in 2009. At the world level, energy consumption was cut down by 1.5% during 2009, for the first time since World War II. Except in Asia and Middle East, consumptions were reduced in all the world regions. In OECD countries, accounting for 53% of the total, electricity demand scaled down by more than 4.5 % in both Europe and North America while it shrank by above 7% in Japan. Electricity demand also dropped by more than 4.5% in CIS countries, driven by a large cut in Russian consumption. Conversely, in China and India (22% of the world’s consumption), electricity consumption continued to rise at a strong pace (+6-7%) to meet energy needs related to high economic growth. In Middle East, growth rate was softened but remained high, just below 4%.

_

The graph below shows electricity consumption per capita country-wise.

You see that India is ranked lowest in the chart above proving the point that India needs sustained development to become a developed nation. Electricity consumption per capita is one of the markers for the development of a society.

_

The figure below shows how world uses electricity:


_

What is a unit of electricity?

Your electricity bill will show the electricity used in ‘units’, the price of each unit is also shown. Ever wondered what a ‘unit’ of electricity is or how long you can run an appliance for on one unit. One unit of electricity is exactly equal to 1000 Watts of power used for 1 hour. So 1 unit is 1 kilowatt-hour.

1 kW hr = 1 unit = 1000 W hr = 1000 J/s hr = 1000 J/s X 3600 s = 3.6 X 106 J or 3.6 million Joules

_

Electricity meter:

An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residence, business, or an electrically powered device. Electricity meters are typically calibrated in billing units, the most common one being the kilowatt hour [kWh]. The most common unit of measurement on the electricity meter is the kilowatt hour [kWh], which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. The meters fall into two basic categories, electromechanical and electronic. AMR (Automatic Meter Reading) and RMR (Remote Meter Reading) describe various systems that allow meters to be checked without the need to send a meter reader out. An electronic meter can transmit its readings by telephone line or radio to a central billing office. Automatic meter reading can be done with GSM (Global System for Mobile Communications) modems, one is attached to each meter and the other is placed at the central utility office. Periodic readings of electric meters establish billing cycles and energy used during a cycle.

_

Growth of electricity:

Demand for electricity grows with great rapidity as a nation modernizes and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century, a rate of growth that is now being experienced by emerging economies such as those of India or China. Historically, the growth rate for electricity demand has outstripped that for other forms of energy.

_

Electricity generation-consumption mismatch:

What happens to excess electricity generated which isn’t used or stored?

Technically there is no such thing as excess electricity. What is produced is consumed. There might be excess generating ‘capacity’, but for the vast majority of the time, generated electric power exactly meets demand. Demand is estimated daily, and over a 24-hour period each day. When demand is estimated low, generators are turned off as necessary, steam generation is throttled back. When demand is estimated higher, more steam is produced; more generators are turned on as necessary. Occasionally demand exceeds estimates, and the possibility of a brown-out might occur. Occasionally demand is less than expected and generators will tend to overrun, so regulators and governers ‘kick in’ to slow them down. Steam for the turbines is then shunted off directly to cooling towers.

_

All normal wires (copper, aluminum, steel, etc.) have some electrical resistance. So a certain amount of power will always have to be used to overcome the resistance of all the wires in a power grid, including wiring in the many transformers, switches, etc. which are needed to distribute the power efficiently. Any power used to overcome the resistance of the wires is dissipated as heat which raises the temperature of the wires, their surrounding insulation (if any) and – in the case of overhead cables – any surrounding air. In the case of an underground or underwater cable which has a cooling fluid such as mineral oil (which is a good conductor of heat yet is also a good electrical insulator) the heat gets dissipated into the cooling fluid which is pumped continuously to allow the heat to be radiated to the air (or to water in, perhaps, a reservoir) using a radiator assembly positioned away from the cable itself. At all times, the net power output being generated at any instant by all the power stations feeding a distribution grid must always be exactly equal to the sum of all the power being demanded by all the loads connected to that grid PLUS the sum of all the power used to overcome the resistance of the grid’s wires. However, there are two things other than power which do change continuously over any given period of time: the supply voltage and the supply frequency. That must be so because a power generator set cannot accelerate or decelerate instantly! Such power generator sets are usually massive alternators driven either by steam turbines (fueled by coal-burning boilers or nuclear power), diesel engines or by water wheels (driven by water falling from a high dam), all of which have very heavy rotating masses that require a finite time to speed up or to slow down. During such periods the supply frequency must be allowed to speed up or to slow down within set limits and the delivered voltage also must be allowed to vary, again within set limits. If there is too much power produced then all that happens is the excess speeds up the turbines, too little power and they slow down and this creates a variation in the supply frequency from that generator (nominally 60Hz in the US)(means motors speed up but that’s about all), too little power and the turbines slow down. In the UK they have a handful of pumped storage schemes where they pump a lake-load of water up a hill when there’s an excess of supply, then allow it to run back down again through turbines to meet short-term peak loads (traditionally during commercial-breaks in popular programs on national television). These pumped-storage power-stations can be turned on and off within a few 10s of seconds. There is provision for quite a high variation in supply voltage before consumers can complain and, when the load gets too much, the frequency can dip, too. In the nature of things, a voltage dip of 6% will supply 12% less power – that would mean there is capacity to deal with additional loads (not more total power – just more connected customers). The reverse is true when people start switching off – the others get higher supply volts. When demand drops, a generator can be designed to respond in two ways. One way is to increase in velocity/rotational speed, thereby transferring unused energy into the rotor. This is not desirable for a number of reasons, not least of which is that it alters the frequency of the mains and plenty of electrical kit is designed for a specific frequency only. The other way is to allow the output voltage to rise a little. Since most of our power is consumed directly as heat – kettles, electric heaters, ovens etc, even old light bulbs are nearly all heat rather than light – increasing the voltage a bit just makes all these things run a bit hotter. So the power dump is distributed over the whole grid. You may have noticed sudden changes in the light levels sometimes. That will be a generator coming on/going off line (or a fault!) and causing the voltage to change as a result of more or less power being available. Also, note that the power used is proportional to voltage squared, so an increase in voltage of 10% will dump around 20% more power. Designing equipment to cope with a wide range in voltage is not a big deal and has always been done, so no problem with that. Nowadays computer-based grid power control systems do match constantly power load with power generation, but human operators are still needed to “keep a close eye on things” to be sure the grid is operating efficiently.  Electricity is produced and then travels in a circuit at the speed of light. Thus the vast majority of electricity is consumed nearly immediately after it is produced. In most cases, the electricity grid is perfectly balanced between production and consumption. In some cases, there is a surplus of power. In those cases, some electricity has to be “spilled”. This can be done by opening a circuit which is directly in contact with the ground. The bottom line is that the power grid, the large system of electric generation and distribution facilities, doesn’t really have a means to store enormous energy.

_

When electricity is sent to homes, how does it ‘know’ if no appliances are connected? Does it go back to the generators again?

Whenever the electric company sends electromagnetic energy to your home, and when you don’t have any appliances plugged in, something interesting occurs. The energy bounces! It reflects from the open ends of the wires and travels back to the big generators, where it’s automatically used to keep them spinning. Because this occurs, the generators won’t slow down much. And that means the electric company won’t have to burn much fuel at all to keep the giant rotors going. But if you turn on all your lights and run all your appliances, then some of the energy stops bouncing when it gets to your house. The big generators start to slow down, so more fuel must be burned to run the steam turbines which keeps the rotors going at their original speed. In truth, those big electric generators can reach out through the wires and feel your appliances. The generators “know” what’s connected. Whenever you plug in a light bulb, the electric company’s generators feel it almost instantly. They feel the extra friction (the electrical friction, not mechanical). Your light bulb uses up some energy, and this means that some of the energy does not get reflected back to the generators. As a result, the generators start to slow down a bit, and more fuel must be burned in order to prevent this. By turning on a light bulb, you can cause a distant nuclear reactor to eat more U-235, or cause a coal-fired boiler to grind up a bit more coal into powder for burning. On the other hand, when you suddenly turn off a light, you create a “dead end” in the energy system. The energy that was sent to your home starts being reflected back to the big generators, and it makes them spin a tiny bit faster. The electric company must then turn down the fires which run the steam turbines to keep the generators from speeding up. They do this quickly, and the changes in generator speed are extremely tiny.

__

So if you are using a simple home power generator and if you are not using the electricity from the generator then what happens with the energy the electricity should hold because of the generator running?

It ends up letting the rotor of the generator run faster (and then the circuit frequency is higher than its nominal value). That is all that happens. Eventually, like all forms of energy, it dissipates as heat loss. You can also actively regulate the speed of the generator such that it controls the fuel flow rate to match the electrical load but it requires a tiny amount of power to keep the control circuit in operation…and that the control system can be expensive to install.

_

Use of electricity:

A kilowatt-hour of electric energy is exactly 3600000 joules. (One watt is the power of one joule of energy (or work) each second of time.) It’s interesting to note that the conversion of electricity to heat is 100% efficient. There is no loss whatsoever.

_

Uses of electrostatics:

_

Static electricity has many practical uses. Photocopiers and laser printers, defibrillators, electrostatic dust precipitators and paint sprayers are all practical applications of static electricity.

_

_

The use of electricity gives a very convenient way to transfer energy, and because of this it has been adapted to a huge, and growing, number of uses. The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories. The Joule heating effect employed in the light bulb also sees more direct use in electric heating. Electricity is however a highly practical energy source for refrigeration, with air conditioning representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate. Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. Optical fiber and satellite communication technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process. The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century, and a fundamental building block of all modern circuitry. A modern integrated circuit may contain several billion miniaturized transistors in a region only a few centimeters square. Electricity is also used to fuel public transportation, including electric busses and trains.

_

Direct conversion of mechanical energy into electrical energy is possible by utilizing the phenomena of piezoelectricity and magnetostriction. These have some application in acoustics and stress measurements. Pyroelectricity is a thermodynamic corollary of piezoelectricity. Pyroelectricity can be visualized as one side of a triangle, where each corner represents energy states in the crystal: kinetic, electrical and thermal energy. The side between electrical and thermal corners represents the pyroelectric effect and produces no kinetic energy. The side between kinetic and electrical corners represents the piezoelectric effect and produces no heat. Piezoelectricity is the charge that accumulates in certain solid materials (notably crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure. The best-known application is the electric cigarette lighter: pressing the button causes a spring-loaded hammer to hit a piezoelectric crystal, producing a sufficiently high voltage electric current that flows across a small spark gap, thus heating and igniting the gas. The portable sparkers used to light gas stoves work the same way, and many types of gas burners now have built-in piezo-based ignition systems.

_

Electric vehicle:

An electric vehicle (EV), also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion. Three main types of electric vehicles exist, those that are directly powered from an external power station, those that are powered by stored electricity originally from an external power source, and those that are powered by an on-board electrical generator, such as an internal combustion engine (a hybrid electric vehicle) or a hydrogen fuel cell. Electric vehicles include electric cars, electric trains, electric lorries, electric aeroplanes, electric boats, electric motorcycles and scooters and electric spacecraft. Due to efficiency of electric engines as compared to combustion engines, even when the electricity used to charge electric vehicles comes from a CO2-emitting source, such as a coal- or gas-fired powered plant, the net CO2 production from an electric car is typically one-half to one-third of that from a comparable combustion vehicle. Electric vehicles release almost no air pollutants at the place where they are operated. In addition, it is generally easier to build pollution-control systems into centralized power stations than retrofit enormous numbers of cars. Vehicles typically have less noise pollution than an internal combustion engine vehicle, whether it is at rest or in motion. Electric vehicles emit no tailpipe CO2 or pollutants such as NO2, NMHC, CO and PM at the point of use. Electric motors don’t require oxygen, unlike internal combustion engines; this is useful for submarines. Electric motors are mechanically very simple. Electric motors often achieve 90% energy conversion efficiency over the full range of speeds and power output and can be precisely controlled. Electric vehicle ‘tank-to-wheels’ efficiency is about a factor of 3 higher than internal combustion engine vehicles. Energy is not consumed while the vehicle is stationary, unlike internal combustion engines which consume fuel while idling.

_


_

UPS:

An uninterruptible power supply (UPS), also uninterruptible power source is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries or a flywheel. The on-battery runtime of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. A UPS is typically used to protect computers, data centers, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss.

_

What is Dirty Electricity?

Over the last decade our AC electrical power supply has become increasingly “dirty”. It’s become contaminated with dangerous radio-frequency radiation – known to cause adverse health – including cancer. This “dirty” electricity is considered by many experts to be the most biologically active electromagnetic pollution, and therefore the most dangerous. This powerful, unnatural electromagnetic energy from outside the body disrupts our body’s critical balance and plays havoc with the millions of electrical impulses that the body uses to regulate all cellular activity. This unnatural energy interferes with our body’s natural processes including sleep, hormone production, our immune system and our ability to heal. All modern electronic devices including computers, TVs, stereos equipment, CFL and low-voltage lighting use transformers and power supplies to convert our relatively clean 60/50 Hz AC current to the low-voltage power used to power all of our today’s modern electronic devices and energy-efficient lighting systems. To save energy these devices use transformers that “chop-up” our conventional AC voltages, using it in short bursts as opposed to a smooth continuous flow of current. This constant stopping and starting of the electrical current causes a combination of what engineers call electrical feedback, in technical terms known as “electrical transients and harmonics”. This electrical pollution rides along on a building’s electrical system with the ability to contaminate an entire home and even buildings and homes nearby. Humans can be exposed to this dangerous EMF energy simply by being in close proximity to a contaminated room or next to electrical devices plugged into AC circuits; we are exposed to this toxin through “capacitive-coupling”. For many, health problems become worse when living and working in an environment contaminated with dirty electricity and other EMF energy.

_

Short circuit:
A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path, often where essentially no (or a very low) electrical impedance is encountered. A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This result in an excessive electric current/overcurrent limited only by the Thévenin equivalent resistance of the rest of the network and potentially causes circuit damage, overheating, fire or explosion. A common type of short circuit occurs when the positive and negative terminals of a battery are connected with a low-resistance conductor, like a wire. With low resistance in the connection, a high current exists, causing the cell to deliver a large amount of energy in a short time. A large current through a battery can cause the rapid buildup of heat, potentially resulting in an explosion or the release of hydrogen gas and electrolyte (an acid or a base), which can burn tissue, cause blindness or even death. Overloaded wires can also overheat, sometimes causing damage to the wire’s insulation, or a fire. High current conditions may also occur with electric motor loads under stalled conditions, such as when the impeller of an electrically driven pump is jammed by debris; this is not a short, though it may have some similar effects. In electrical devices, unintentional short circuits are usually caused when a wire’s insulation breaks down, or when another conducting material is introduced, allowing charge to flow along a different path than the one intended. In mains circuits, short circuits may occur between two phases, between a phase and neutral or between a phase and earth (ground). Such short circuits are likely to result in a very high current and therefore quickly trigger an overcurrent protection device. However, it is also possible for short circuits to arise between neutral and earth conductors, and between two conductors of the same phase. Such short circuits can be dangerous, particularly as they may not immediately result in a large current and are therefore less likely to be detected. Damage from short circuits can be reduced or prevented by employing fuses, circuit breakers, or other overload protection, which disconnect the power in reaction to excessive current.

_

High voltage:

As far as human safety is concerned, “High voltage” is any voltage which can injure or kill. Some safety organizations consider 60V to be dangerous, and everything above 60V is called “high voltage.” Others put the threshold at 40V. If you soak your skin with salt water and then solidly connect yourself to a DC circuit by grabbing some metal bars, you can probably injure yourself with forty volts. There is another meaning for “high voltage:” any voltage which can cause sparks to jump through air. The tiniest sparks begin to be seen at voltages between 500V and 700V, so anything above these values can be considered as “high voltage.”

_

Plugging a 115 volt device in a 220 volt circuit will probably destroy the device. Plugging a 220 volt device in a 115 volt circuit will destroy the wiring if not properly protected, and may cause a fire.

_

What is the difference between fire and electricity? What is the role of electricity in combustion? Why is electricity prone to cause fires?

There is all the difference in the world between electricity and fire. Fire is the result of a chemical reaction, a chemical reaction that produces heat and light. Not all chemical reaction produce heat and light and some only produce heat and some only produce light. Electricity is the result of charged particles either in motion (an electrical current) or not (static electricity). In most cases for a fire to start there must be a quantity of heat energy available to get the chemical reaction started. Once started the chemical reaction can sustain itself until it runs out of fuel or oxygen. In most cases an electrical current will produce heat and if it produces enough heat it can start the combustion process and there is a fire. Static electricity can produce a lot of heat when it discharges. The best example of this is lightening. This too can start a fire. So, electricity can start a fire only if it produces enough heat to get the chemical reaction going. But the two, electricity and fire, are still very, very different from each other. Electricity is the transfer of electrons along a wire; fire is the reaction of a substance with oxygen. A yellow flame, as usually observed, is an area filled with hot carbon particles that can cause other substances to ignite. An electric spark is an area where the air conducts electricity by ionization. These sparks may ignite combustible materials. Also, a wire that has a current flowing through it may heat-up and cause the temperature to rise sufficiently to ignite materials. This heating up effect is more severe when the current (I) is higher, so in a short-circuit circumstance (where the resistance of a circuit becomes nearly zero and the current blows up according to V = IR) the heating may cause a fire, which is the main electricity fire hazard in household.

_

What happens if you connect phase with neutral directly in your AC mains circuit?

When I was 10 year old child, I was warned by my engineer father not to touch electric socket and also not connect hot wire (phase) with neutral. I was very curious and inquisitive at that age. One evening I found a small wire and I connected phase with neutral in the socket and switched on power. There was a small blast with spark and that small wire got burned. I luckily escaped any injury. When accidentally you connect phase with neutral, the connecting thing is not a resistor and hence very large current of hundreds of amperes flow resulting in overheating wires, spark and a small blast. It is dangerous.

_

Why can birds land on power lines without harm?

The charges would rather go straight through the wire, rather than taking a detour through the bird! Bird skin is a poor conductor, but copper has thousands of times more conductivity. If a robot bird made of metal landed on a power line, then there would be charges flowing through the metal bird.

_

Stay safe:

The electrical engineer’s maxim: The smoke that escapes from a device or a component is its spirit without which it cannot work. In other words: if smoke rises from the device, then it’s destroyed. The first time you use electrical equipment on a voltage system you haven’t used before, watch for excessive heat, strange smells, and smoke. This is especially true for those residing in countries with 120V (USA, Canada, Japan, etc.) visiting places with the higher voltage. Smoke is a sure sign your equipment cannot cope with the voltage system. If your electrical equipment gets very hot, smells of burning (there is a distinct smell of electrically fried circuit boards) or starts to smoke, turn it off at the wall or the main switch immediately, then carefully unplug the equipment. Do not disconnect or unplug by just grabbing the smoking device, its plug or cord, and then unplugging it, as these parts are probably very hot, and the insulation could be melted or unsafe, which could result in electrocution. You may find your expensive equipment has been fried and needs to be replaced because the wrong voltage was used. However, if the equipment only got hot and did not smoke or produce strange burning smells you may be lucky. Some older devices have fuses that you may be able to replace. New devices, such as gaming consoles, will trip a circuit breaker. Disconnect them from all power and leave them for 60 minutes or so, and the circuit breaker will normally reset. Do not rely on fuses to protect your equipment. If a fuse does blow, you should have things checked by an electrician before using the suspect equipment again. In Third World countries with frequent blackouts, it’s not at all uncommon for a visitor to plug something in and have the power go out coincidentally. Always check the neighborhood first, before blaming the appliance or looking at the fuse/circuit breaker.

_

Electric shock:

Electric shock occurs upon contact of a (human) body with any source of electricity that causes a sufficient current through the skin, muscles, or hair. Typically, the expression is used to describe an injurious exposure to electricity. The word “electrocution” eventually took over as a description of all circumstances of electrical death from the new commercial electricity. The word is often used incorrectly as a synonym of electric shock. The voltage necessary for electrocution depends on the current through the body and the duration of the current. Ohm’s law states that the current drawn depends on the resistance of the body. The resistance of human skin varies from person to person and fluctuates between different times of day. The NIOSH states ‘Under dry conditions, the resistance offered by the human body may be as high as 100,000 Ohms. Wet or broken skin may drop the body’s resistance to 1,000 Ohms,’ adding that ‘high-voltage electrical energy quickly breaks down human skin, reducing the human body’s resistance to 500 Ohms.’ Electric shock can cause electric burn at entry and exit would, ventricular fibrillation and neurological effects.

_

Electric currents cause harm when the charges in your body are forced to flow. Yet both batteries and wall outlets can pump a large electric current. But it’s not their current-making ability that causes electrocution. Flashlight batteries can put out several amperes, yet batteries are safe because human skin is a relatively bad conductor. It takes a fair amount of electric voltage in order to force the charges within your body to start flowing. Touch both terminals of a D-cell, and the electric current in your skin will be so tiny that you can’t feel anything. On the other hand, metal wires aren’t like skin, and it only takes a tiny voltage to pump electric charge through a flashlight bulb. Because the voltage of a D-cell is very low, it can only create large currents in wires and in light bulbs, but not in people. Now if 1.5 volts from batteries is safe, then what level of voltage is “dangerous?” The answer: it varies from person to person, but serious danger only appears when the voltage is higher than about 40 volts. This has little to do with AC versus DC. However, all else being equal, AC is more dangerous than DC because AC has a slightly greater effect upon your heart in causing fibrillation. Humans are electrically protected by their skin. Here’s a disgusting thought: remove your skin, and even a battery becomes a danger! If you have a big cut in your chest, don’t go sticking a 9-volt battery into it. If you have huge cuts on your hands, then don’t grab the terminals of a car battery. It could stop your heart! Flowing charge inside your body is dangerous, but it takes a voltage to create a charge-flow. A flashlight battery is probably not dangerous because the 1.5 volts can’t create a large current in your heart. On the other hand, high voltage by itself is not dangerous. For example, if you slide across a car seat and then climb out of the car, 20,000 volts can appear between your body and the car! Touch the car, and you feel a painful spark, but you certainly aren’t in danger of dying. High voltage was present, but there weren’t any continuous electric currents. You can scuff your shoes on the rug and zap doorknobs all day with little harmful effect, even though the voltage occasionally approaches 10,000 volts. Everyday “static” sparks are not very dangerous, since the high voltage instantly vanishes when the spark occurs, and it cannot produce a large, continuing flow of charge through your body. To be dangerous, an electrical energy source needs to be above 40 volts so it can get through your skin. Also the energy source needs to be able to supply a large current for a long time (for at least a few seconds.). People are harmed by electric current mostly because the current can stop your heart. High current can also cook your body or cause lethal chemical changes in your muscles. But human skin is a poor conductor. It takes a fairly high voltage in order to push a fast flow of charges through a human body. Voltage is like a “push”. Voltage causes current. Voltage alone cannot hurt you. However without high voltage, electrocution could not occur. The voltage is the “pressure” that causes charges in your body to flow along, and it takes more than about 40 volts in order to push a big enough current through your body to severely shock you. So, if a power supply is rated in volts and amps, which one is the danger? BOTH. In order to be dangerous, the power supply voltage must be higher than 40 volts, and the current rating must be higher than about ten milliamps (1/100 ampere.) At a much lower current than this, even a high voltage power supply cannot electrocute you. And if the power supply voltage is well below 40V, it’s not dangerous even if the current rating is very high.

__

The lethality of an electric shock is dependent on several variables:

1. Current: The higher the current, the more likely it is lethal. Since current is proportional to voltage when resistance is fixed (ohm’s law), high voltage is an indirect risk for producing higher currents.

2. Duration: The longer the duration, the more likely it is lethal — safety switches may limit time of current flow

3. Pathway: If current flows through the heart muscle, it is more likely to be lethal.

4. Very high voltage (over about 600 volts): This is an additional risk over the simple ability of high voltage to cause high current at a fixed resistance. Very high voltage, enough to cause burns, will cause dielectric breakdown at the skin, actually lowering total body resistance and, ultimately, causing even higher current than when the voltage was first applied. Contact with voltages over 600 volts can cause enough skin burning to decrease the total resistance of a path though the body to 500 ohms or less.

__

The hazards of electricity (as seen in table below) depend on the amount of electrical current, its frequency, its duration, its path through the body, and the physical condition of the person. Alternating current at 60/50 Hz is slightly more dangerous than direct current, but high frequency currents (greater than a few kHz) are safer because they tend to flow on the surface of the skin and away from the heart and lungs. The resistance of the body varies from about 300 ohms to about 100,000 ohms, and thus even very low voltages can produce lethal shocks. Fatalities have occurred at voltages as low as 24 volts. For currents that exceed the “let-go” current (10-20 mA) the person becomes frozen to the circuit, and the current typically rises to a level of about 25 mA where muscular contractions onset. Then the person is either thrown clear of the circuit or the current continues to rise until ventricular fibrillation or cardiac arrest occurs (at 50-200 mA), assuming the path of the current is through the heart.

_

Average Effects of Continuous AC or DC Electrical Currents on Healthy Adults:

Electrical Current Biological Effect
1 mA threshold for feeling
10 – 20 mA voluntary let-go of circuit impossible
25 mA onset of muscular contractions
50 – 200 mA ventricular fibrillation or cardiac arrest

_

Power outage:

Power outage (also power cut, blackout, or power failure) is a short- or long-term loss of the electric power to an area. There are many causes of power failures in an electricity network. Examples of these causes include faults at power stations, damage to electric transmission lines, substations or other parts of the distribution system, a short circuit, or the overloading of electricity mains. Power failures are particularly critical at sites where the environment and public safety are at risk. Institutions such as hospitals, sewage treatment plants, mines, and the like will usually have backup power sources such as standby generators, which will automatically start up when electrical power is lost. Other critical systems, such as telecommunications, are also required to have emergency power. Telephone exchange rooms usually have arrays of lead-acid batteries for backup and also a socket for connecting a generator during extended periods of outage.

_

India’s electricity crisis (read prologue):

The official explanation for the world’s worst blackout on 30th and 31st July 2012 — weak monsoon rains translating to lower power generation, hotter temperatures and more air conditioning demand. A major reason for the outage was a surge in demand from farmers. More farmers were relying on electric pumps to get to ground water because of the failure of this summer’s monsoon rains. India’s provinces get power for their local grids via the more than 100,000 kilometers of national lines operated by Power Grid. One of two major transmission lines in northern India was shut for work at the time, forcing power onto a single line. The entire load fell on one line and that led to the cascading effect. The country has a shortage of generating capacity – reported as 8 percent. But the peak power shortfall is much more severe — in excess of 14 percent. The grid is outdated.  Of the 620 million people in the region that lost power, about 200 million don’t have any electricity to begin with. Another 100 million are in wired villages where actual electrons are an occasional, but not necessarily even a daily, event — they have spasmodic power. The remaining 300 million urban or small town customers lose power frequently on hot summer afternoons when demand peaks. So being without power is not a new experience in homes and businesses, but when the whole grid goes down even normally protected users, like railroads and water treatment plants, shut down. And these users, unlike most businesses, can’t rely on back-up diesel generators.

_

India is both a major energy producer and consumer. India currently ranks as the world’s eleventh greatest energy producer, accounting for about 2.4% of the world’s total annual energy production, and as the world’s sixth greatest energy consumer, accounting for about 3.3% of the world’s total annual energy consumption. Despite its large annual energy production, India is a net energy importer, mostly due to the large imbalance between oil production and consumption. India is presently the sixth-greatest electricity generating country and accounts for about 4% of the world’s total annual electricity generation. India is also currently ranked sixth in annual electricity consumption, accounting for about 3.5% of the world’s total annual electricity consumption. Overall, India’s need for power is growing at a prodigious rate; annual electricity generation and consumption in India have increased by about 64% in the past decade, and its projected rate of increase (estimated at as much as 8-10% annually, through the year 2020) for electricity consumption is one of the highest in the world. Lowering energy intensity of GDP growth through higher energy efficiency is the key to meeting India’s energy challenge and ensuring its energy security. India’s energy intensity vis-à-vis GDP growth has been falling and is about half what is used to be in early 70s. Energy consumption, per unit of GDP in purchasing power parity terms is only 0.19 kilogram oil equivalent per dollar as compared to 0.21 of the world average. But there is a still room for improvement and can be brought down further significantly with current commercially available technologies. Despite of a reasonable growth in GDP and dependence on fossil fuels to meet the Energy needs of India, carbon dioxide emission per capita in India is still low, i.e., around 1 ton against the world average of about 4 ton and of about 19 tons in case of some developed countries (According to IEA). The electricity sector in India had an installed capacity of 202.98 Gigawatt (GW) as of May 2012, the world’s fifth largest. Captive power plants generate an additional 31.5 GW. Thermal power plants constitute 66% of the installed capacity, hydroelectric about 19% and rest being a combination of wind, small hydro, biomass, waste-to-electricity, and nuclear. India generated 855 BU (855 000 MU i.e. 855 TWh) electricity during 2011-12 fiscal. In terms of fuel, coal-fired plants account for 56% of India’s installed electricity capacity, compared to South Africa’s 92%; China’s 77%; and Australia’s 76%. After coal, renewal hydropower accounts for 19%, renewable energy for 12% and natural gas for about 9%.

_

At root the Indian energy system suffers a problem of under-capacity. Output is reported to have increased by 35 per cent over the past five years which sounds impressive, but demand has been rising at 6.5 to 8.5 per cent per year. Demand overshoots supply by a fifth during peak demand. A weak monsoon won’t have helped hydro-electricity generation, ageing infrastructure and pervasive electricity theft create widespread leakages, and there have been shortfalls in supplies of coal and gas. However, a failure of this size is always political as well as technical, and a number of commentators are pointing the finger towards stalled reforms of the energy sector. Research by the Eurasia Group points to underinvestment in all aspects of the electricity system, from generation to transmission to distribution. The state-backed Coal India maintains a near monopoly over coal supply, which accounts for over half India’s commercial energy. As world’s largest coal producer, it supplies 82 out of India’s 86 coal based thermal power plants, but its inability to meet demand has forced operators to rely on expensive imports. Power generators then find themselves unable to adjust their prices in line with their raised input costs – energy pricing policies are developed at state level, where governors have kept consumer tariffs low. The state electricity boards which purchase the energy frequently run at a loss, deterring new infrastructural investment – so new power sources don’t have the corresponding grid to transmit effectively. Companies must be able to recover their costs, especially as those costs are going to rise as coal and gas become more expensive. However, state governors fear the political consequences of raised energy prices, particularly among the politically powerful farming communities who currently receive heavily subsidized power. Electricity is a very political issue. Subsidized electricity to farmers is also exacerbating electricity-supply bottlenecks, discouraging producers from adding capacity. India deliberately abandoned metering power supply for agricultural irrigation in the 1970s, as part of a strategy of switching to new high-yield crops, which required regular water supplies. Prices of energy, including power, diesel and kerosene, are sensitive issues in India where about 800 million people live on rupees 20 per day i.e. less than half dollar per day. Price increases are often opposed by political parties and spark street protests. Populist state governments don’t want to raise tariffs, but in Tamilnadu, Kerala and Karnataka the political will have been high and they have pushed the reforms through. However, the higher rates mainly apply to higher power users, so the impact on the poor is less – “otherwise there would be a lot of political opposition.”

_

The electricity network in Asia’s third-largest economy loses 27 percent of the power it carries through dissipation from wires and theft, while peak supply falls short of demand by an average of 9 percent, according to India’s Central Electricity Authority. Some 300 million people in India, or one in every four, remain without links to the grid and the number will still be about 150 million by 2030, according to the Paris-based International Energy Agency. Large Indian companies have created their own islands as they can’t rely on a precarious state power network. Five of India’s biggest electricity users generate 96 percent of their requirement, according to their annual reports.

_

The most serious bottleneck in generation is the shortage of coal. At the end of 2007, the gap between the demand and supply of coal was 35 million tons. It is expected to be around 83 million tons at the end of 2012. The shortage would have been even more had all the planned coal-based power plants been commissioned on time. By 2017, the shortage is forecast to be 200 million tons. Some of the blame for the shortage can be laid at the door of the environment minister whose controversial ‘no-go’ policy announced in 2009 imposed a ban on mining in heavily forested areas. It declared 35 per cent of forest area in nine major coal-mining zones as ‘no-go’ zones. That led to an immediate halt of mining activity in 203 blocks which had a potential capacity of over 600 million tons. Coal Ministry argued that this ban could affect power generation to the tune of 130000 MW. Also, on average, Indian power plants uses 0.7 kg of coal to generate 1 kWh while countries like US consume 0.45 kg of coal per kWh. So India has to improve its energy efficiency in generating electricity.

_

India doesn’t primarily need more centralized, base-load power plants — it needs to modernize its entire power system. It needs to recalibrate power policy to recognize that electricity is a social good, which requires intelligent social management to fulfill its promise. Not all electrons are created equal — those produced reliably and cleanly, immune to fuel price increases, and locally and efficiently generated and used, are the most valuable. These sources, unlike India’s present suite of imported coal, fossil fuel subsidies, stolen power and politicized electricity giveaways, would not bankrupt its treasury to increase its trade deficit on oil and coal. The vicious cycle that is now afflicting the world’s biggest democracy could become a virtuous one which restored its development trajectory — but without the devastating health, environmental and financial costs of over-dependence on fossil fuels. Recent reports have estimated that India has enough wind potential alone to meet its electricity needs for the foreseeable future – ignoring solar, biomass and other sources. Energy efficiency is the other big untapped potential – efficiency measures in the appliance, agriculture and industry sectors, along with a reduction in transmission and distribution losses can result in a saving of 255 billion kWh for India, according to the Indian Government’s Interim Report of the Expert Group on Low Carbon Strategies for Inclusive Growth. The writing is on the wall, and savvy investors are reading it clearly – coal is dying, renewables are on an upswing.

_

India could also look forward to utilize its abundant thorium deposits in the place of coal, which serves as the major source of electricity generation in the country. The nation has an estimated thorium deposit of 650,000 tons which is more than one-fourth of the total deposit in the world. India produces 70% of electricity from fossil fuels which has got a negative impact on the environment. Coal remains preferable in over generation though above 40% is imported, but on the contrary it disturbs the environment with Green House Gas (GHG) emissions. Nuclear energy caters only 3 % of overall energy requirements of India, currently. Shortage of coal resources and the environmental issues raised by it, difficulties in constructing dams for hydro electricity etc. adds to the reliance and construction of nuclear power plants.

_

Smart grid technologies can revolutionise electricity management in India:

The traditional grid was about engineering — making enough power flow safely through the system. Today, however, we need highly improved management and control mechanisms. In essence, we need a “smart grid”. A smart grid has no single definition and isn’t one single technology; it involves the use of digital communications and control to transform the grid to be more resilient, nimble, renewable-friendly and efficient. Improvements in information and communication technologies allow us to make grid measurements and control almost real-time. For many, this starts with a smart meter. It has advanced bi-directional communication and control (connect/disconnect) facilities, which enable us to know in almost real-time where the power is going. This can help cut down theft and other losses. But there is more this technology can do. What smart grids can deliver is driven by need. Considering that electricity cannot easily be stored in large scale, one has to either increase supply or reduce demand. Increasing supply is what the West does today, through the use of “peaker” units, which operate on fast-starting fuels like diesel or open-cycle gas turbine (or hydro turbine). Such a plant only operates during the peak, for a fraction of the time, so its electricity is inherently expensive. Consumers in the West typically don’t see such peak costs since the final tariff is a blended one, with the exception of larger bulk consumers or selected newer systems with variable tariffs. We estimate that if India were to add peakers (which may come to around Rs 7-8/kWh), and blend this, the average supply cost might increase by over 35 per cent. The alternative is to reduce demand, not merely through demand-side management, which includes efforts like solar water heaters and compact fluorescent lamps, but by a dynamic system that reduces demand when and where required. This can be achieved through a “demand response”. We should, therefore, no longer think of a kilowatt-hour of electricity being the same as every other kilowatt-hour. To extend an analogy by Peter Fox-Penner in his book Smart Power, people today think of electricity as buying fruit. They buy it at, say, Rs 4 per unit. But in reality, that basket of goods is a mix of different fuels and different costs. Though the “fruit” is made of bananas, apples, mangoes and so on, including some expensive and some seasonal items, the blend remains hidden. In fact, not only are we blending costs, by hiding from consumers the true marginal costs of electricity, we are selling the same basket to different consumers at different prices. This isn’t just about subsidies to agricultural users versus higher rates to commercial users — even within residential users we charge differently, based on the total monthly consumption. But from a system perspective, whether one uses 50 or 100 units of total power is less important than when that power is consumed. This needs to change and a smart grid can enable this change.

_

Nano tech to solve power crisis in India:

Nano technology is the panacea for India’s growing power crisis, predicted Dr Vijayamohanan Pillai, Director of Central Electro Chemical Research Institute (CECRI), Karaikudi. He was delivering the 65th Foundation Day lecture at the Central Leather Research Institute (CLRI ) at Guindy. The growing energy needs of India need to be addressed in the light of the fact that it has a vast growing population. Given the acute power shortage the state is facing today, nano technology will provide economically viable solutions to the crisis, he said on an optimistic note. Dr Pillai, who made a presentation on ‘Advances in nanomaterials and their impact on energy technology’, stated that the solar power cells and nano cells could solve the energy crisis of the future. India is committed to generate 20 gigawatts of electricity by the year 2020, he stated emphatically.

_

India’s Electricity Transmission and Distribution Losses:

The total power generation in the country is around one lakh (100000) MW of which billing was done only for 55,000 MW and the rest 45,000 MW was going as pilferage and power theft. Out of 45,000 MW, the annual power theft was around 30,000 MW causing a financial loss of Rs 200,000 million to the nation’s exchequer every year. As much as 40% of the power generated in India is not paid for. The bulk of it is stolen. According to World Resources Institute (WRI), India’s electricity grid has the highest transmission and distribution losses in the world – a whopping 27%. Numbers published by various Indian government agencies put that number at 30%, 40% and greater than 40%. This is attributed to technical losses (grid’s inefficiencies) and theft.

_

Theft, in Delhi, accounts for 42% losses. For those who don’t understand how power theft actually happens, the photograph below is illustrative.


_

By contrast, China apparently loses just 3% of its electricity to theft as part of 8% total power transmission losses. OECD countries’ transmission and distribution losses are just 7%.

_

Power theft via ultra-modern device in India:

The device generated an electrostatic discharge. It was the size of a compass box used by school students. The user could keep it anywhere and only when he wanted to tamper with the meter does he have to fit a wire loop and place the device and the loop near the meter. The device has an electronic circuit and a coil, which get activated on pressing a small button. The device produces high voltage and high frequency discharge, which creates a small spark in the meter. The meter gets ‘hanged’ and does not record electricity consumption. When the user wants the meter to function normally, he reactivates it using the same method. The most shocking aspect of the device is that it does not leave any evidence of theft.

_

Radio frequency meters to check power theft in homes:

The system works on the principle of mobile technology. It comprises a radio frequency meter in which the staff of the sub-station concerned inserts a SIM card prior to installation. After this the meter is connected to a modem installed at the sub-station. To download information about the consumption pattern of consumers, the modem operator would dial the particular SIM card number to gain access to the information related to the total consumption by the said consumers. The entire information would be downloaded and transferred to the laptop of the sub-divisional officer, executive engineer, superintending engineer and the chief engineer. This system, apart from maintaining transparency, would make it difficult to tamper with the electricity meter because the department can keep a tab over its working. The sophisticated instrument would also maintain a record of non-use of electricity even during regular power supply. Apart from this, it would also provide reprieve to the overburdened staff from visiting every house for taking meter reading as the same can be done at the substation using a meter reading instrument.

_

Japan must solve power shortage to host Games:

International Olympic Committee president Jacques Rogge said that Japan’s wavering power supply is a concern for hosting the 2020 Games. “We know that the disaster of Fukushima has had an effect on the power supply, because nuclear power has been shut down and so in times of peak consumption there might be a shortage of power,” Rogge said. “The IOC will follow the evolution and we trust the Japanese will find a solution for that. They’re one of the most important economies of the world so we believe they can handle that.” The resource-poor country used to draw about one-third of its electricity from atomic power, but last year’s tsunami-sparked meltdown at the Fukushima Daiichi plant has generated anti-nuclear sentiment among a wary public. Japan’s 50 commercial reactors have all been switched off, and when — or if — they will be restarted remains uncertain.

_

Light bulb and electricity:
_

Ordinary light bulb-incandescent bulb:


_

CFL bulb:


_

LED bulb:


_

Almost half of the electricity used by industry is for lighting. In homes, up to 25 percent of our electric bill is for lighting. Most of the light is produced by incandescent light bulbs, using the same technology developed in 1879 by Thomas Edison. These bulbs are surprisingly inefficient, converting up to 90 percent of the electricity they consume into heat. If the country converted to new technologies, the electricity consumed to produce light could be reduced by up to 70 percent! This would lower carbon dioxide emissions equivalent to removing one-third of the nation’s cars from the highways. Reducing the electricity consumed by just one percent would eliminate the need for an average-sized power plant. Recent developments have produced compact fluorescent lights (CFLs) that are four times as efficient as incandescent bulbs and last up to ten times longer. These new bulbs fit almost any socket, produce a warm glow and, unlike the earlier models, no longer flicker and dim. Over the life of the bulbs, CFLs cost the average consumer less than half the cost of traditional incandescent bulbs for the same amount of light.

__

A “normal light bulb” is also known as an incandescent light bulb. These bulbs have a very thin tungsten filament that is housed inside a glass sphere. They typically come in sizes like “60 watt,” “75 watt,” “100 watt” and so on. The basic idea behind these bulbs is simple. Electricity runs through the filament. Because the filament is so thin, it offers a good bit of resistance to the electricity, and this resistance turns electrical energy into heat. The heat is enough to make the filament white hot, and the “white” part is light. The filament inside a light bulb is much thinner than the wires that lead up to the bulb. The charges flow slowly in thick wires, but they must flow fast in the thin filament. Charges experience a kind of “electrical friction”, and when they flow faster, more heat appears. This friction experienced by the fast charges heats up the filament. The same kind of “friction” heats up all wires, but the charges flow slowly in thick wires, so this heating is usually not enough to even notice. The same kind of friction heats up the wires inside of toasters and electric heaters. In that case, the heating isn’t enough to make the wires glow white hot like a light bulb filament. Instead they just glow red or orange. The filament glows because of the heat — it incandesces. The problem with incandescent light bulbs is that the heat wastes a lot of electricity. Heat is not light, and the purpose of the light bulb is light, so all of the energy spent creating heat is a waste. Incandescent bulbs are therefore very inefficient. They produce perhaps 15 lumens per watt of input power.

_

A fluorescent bulb uses a completely different method to produce light. There are electrodes at both ends of a fluorescent tube, and a gas containing argon and mercury vapor is inside the tube. A stream of electrons flows through the gas from one electrode to the other (in a manner similar to the stream of electrons in a cathode ray tube). These electrons bump into the mercury atoms and excite them. As the mercury atoms move from the excited state back to the unexcited state, they give off ultraviolet photons. These photons hit the phosphor coating the inside of the fluorescent tube, and this phosphor creates visible light. A fluorescent bulb produces less heat, so it is much more efficient. A fluorescent bulb can produce between 50 and 100 lumens per watt. This makes fluorescent bulbs four to six times more efficient than incandescent bulbs. That’s why you can buy a 15-watt fluorescent bulb that produces the same amount of light as a 60-watt incandescent bulb.

_

Light Emitting Diodes (LEDs) create light in much the same way as fluorescent tubes or neon signs. In an LED’s crystal the electrons of its atoms are pumped up to higher energy states. When they fall back down again, each atom gives off a particle/wave of light. However, the electrons in an LED are not exactly the same as the ones in gas molecules in a neon sign. LED electrons aren’t in orbitals stuck to individual atoms. Instead the electrons occupy a contiguous “sea of charge,” and they continually wander among all the atoms in the crystal material. But while they do this, they maintain a particular energy level just like they do when stuck to individual atoms. It’s as if each electron in an LED crystal was “orbiting” among all the atoms of the substance as a whole, and each electron always “orbits” at a particular “height” above each of the atoms it passes. To create LED light, first we connect two conductive crystals of different characteristics together. Both types of crystal contain movable electrons. In one type of crystal the electrons “orbit” naturally at a high energy level, and in the other, they always “orbit” low. When a voltage is applied across the joined crystals, the electrons inside are forced to flow across the boundary between the pair of crystals. If the flow direction is correct, electrons in the “high” crystal flow into the “low” crystal and must begin orbiting at the lower energy level. As they fall to the lower energy level, they give off light. The frequency of the light (which we see as color) is determined by the difference in energy levels between the two crystals. By manufacturing different types of crystals having different natural energy levels, various colors of light can be created. Crystals with similar levels create low-energy photons of red light or even infrared light. With a larger difference in energy levels, green light can be created. An even larger energy-step can create blue light, or violet, or UV.

__

The electricity used over the lifetime of a single incandescent bulb costs 5 to 10 times the original purchase price of the bulb itself. Light Emitting Diode (LED) and Compact Fluorescent Lights (CFL) bulbs have revolutionized energy-efficient lighting. Compared to general-service incandescent lamps giving the same amount of visible light, CFLs use one-fifth to one-third the electric power, and last eight to fifteen times longer. A CFL has a higher purchase price than an incandescent lamp, but can save over five times its purchase price in electricity costs over the lamp’s lifetime. CFLs typically have a rated lifespan of 6,000 to 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours. Because the eye’s sensitivity changes with the wavelength, the output of lamps is commonly measured in lumens, a measure of the power of light as perceived by the human eye. The luminous efficacy of lamps is the number of lumens produced for each watt of electrical power used. The luminous efficacy of a typical CFL is 50–70 lumens per watt (lm/W) and that of a typical incandescent lamp is 10–17 lm/W. Compared to a theoretical 100%-efficient lamp (680 lm/W), these lamps have lighting efficiency ranges of 9–11% for CFLs and 1.9–2.6%, for incandescents. Fifty to seventy percent of the world’s total lighting market sales were incandescent in 2010. Replacing all inefficient lighting with CFLs would save 409 terawatt hours (TWh) per year, 2.5% of the world’s electricity consumption. In the US, it is estimated that replacing all the incandescents would save 80 TWh yearly. Since CFLs use much less energy than incandescent lamps (ILs), a phase-out of ILs would result in less CO2 being emitted into the atmosphere. Exchanging ILs for efficient CFLs on a global scale would achieve annual CO2 reductions of 230 Mt (million tons). By way of comparison, this is greater than then combined yearly CO2 emissions of the Netherlands and Portugal. Solid-state lighting using light-emitting diodes (LEDs) now fills many specialist niches such as traffic lights. Recent consumer availability of household LED lights now competes with CFLs for high-efficiency house lighting as well. LEDs providing over 200 lm/W have been demonstrated in laboratory tests and expected lifetimes of around 50,000 hours are typical. The luminous efficacy of available LED lamps does not typically exceed that of CFLs, though there have been LED lamps available for purchase with better than 90 lm/W overall luminous efficacy at least since early 2012. U.S. Department of Energy (DOE) tests of commercial LED lamps designed to replace incandescent or CFLs showed that average efficacy was still about 30 lm/W in 2008 (tested performance ranged from 4 lm/W to 62 lm/W). A 10-watt LED bulb (which glows white when turned on) could save the America about 35 terawatt-hours of electricity or $3.9 billion in one year and avoid 20 million metric tons of carbon emissions if every 60-watt incandescent bulb in the U.S. was replaced with the LED bulb.

_

LED

CFL

Incandescent

Light bulb projected lifespan

50,000 hours

10,000 hours

1,200 hours

Watts per bulb (equiv. 60 watts)

10

14

60

Cost per bulb in US

$35.95

$3.95

$1.25

KWh of electricity used over
50,000 hours

300 – 500

700

3000

Cost of electricity (@ 0.10per KWh) in US

$50

$70

$300

Bulbs needed for 50k hours of use

1

5

42

Equivalent 50k hours bulb expense

$35.95

$19.75

$52.50

Total cost for 50k hours

$85.75

$89.75

$352.50

Frequent On/Off Cycling

no effect

shortens lifespan

some effect

Turns on instantly

yes

slight delay

yes

Durability

durable

fragile

fragile

Heat Emitted

low (3 btu’s/hr)

medium (30 btu’s/hr)

high (85 btu’s/hr)

Sensitivity to temperature

no

yes

some

Sensitivity to humidity

no

yes

some

Hazardous Materials

none

5 mg mercury/bulb

none

Replacement frequency
(over 50k hours)

1

5

40+

_

If a 150 lm/Watt Solid State LED source were developed, then in the United States alone we would:

1. Realize $115 Billion cumulative savings by 2025

2. Alleviate the need for 133 new power stations

3. Eliminate 258 million metric tons of carbon

4. Save 273 TWh/year in energy

_

Electricity consumption from electronic devices such as laptops and mobile phones could be cut by more than half through the use of the best available technology.

_

ACs consume 40% of your utility bills – choose wisely!

_


The figure above shows average distribution of power utility bills. Current estimates indicate that nearly 40% of an average family’s power consumption comes from cooling! So how do you go about selecting an energy efficient AC system to help you keep your cool this summer, without burning a hole in your pocket?

_

How much power a 1 Ton split AC consume a month?

The question of the amount of power consumed by a 1 ton split AC in a month cannot be answered precisely. This depends upon EER and BTU of the brand of AC and only guesses can be made. In general, 1 ton AC with EER of 10 and BTU of 19000 may power 1000 watts. In that case it can be presumed that it can consume up to 1 unit of electricity every hour. So if the AC works for 10 hours a day, power consumption will be 10 units. But a couple of hours of electricity consumption have to be deducted as the thermostat would cut off the working of the compressor as the required cooling is obtained. In that case the net consumption may be about 8 units every night. When multiplied by 30 days, the consumption comes to be 240 units each month.

_

Standby power waste:

Most experts agree that standby power is electricity used by appliances and equipment while they are switched off or not performing their primary function. That power is consumed by power supplies (the black cubes—sometimes called “vampires”—converting AC into DC), the circuits and sensors needed to receive a remote signal, soft keypads and displays including miscellaneous LED status lights. Standby power use is also caused by circuits that continue to be energized even when the device is “off”. A large number of electrical products – from air conditioners to VCRs – cannot be switched completely off without unplugging the device or turning it off at a power strip. These products draw power 24 hours a day, often without the knowledge of the consumer. When appliances such as VCRs, DVDs and cell phone chargers are plugged into the wall, they consume energy even when the product is not in use. Consumers often believe that their appliance is off, when in fact it is standing by and still consuming power. We call this power consumption “stand-by power”. According to Lawrence Berkeley National Laboratory, in particularly inefficient designs, the stand-by power use can be as high as 15 or 30 watts. For a single appliance, this may not seem like much, but when we add up the power use of the billions of appliances in the United States, the power consumption of appliances that are not being used is substantial. It is estimated by International Energy Agency that 5 to 15% of household electricity consumption worldwide is wasted in standby mode. Up to 90% of standby power is wasted energy consumed by inefficient power supply designs and unnecessarily energized components. The Lawrence Berkeley National Lab estimates that a 75% reduction is possible in new equipment and that nearly all standby functions can be performed with a total appliance standby power of one watt or less. This can be achieved by using improved power supply technologies and designs, namely, by replacing inefficient linear power supplies with smarter switch-mode power supplies.

_

Advantages of standby power:

Standby power is often consumed for a purpose, although in the past there was little effort to minimize power used.

1. It may enable a device to switch on very quickly without delays that might otherwise occur (“instant-on”). This was used, for example, with CRT television receivers (now largely supplanted by thin solid-state screens), where a small current was passed through the tube heater, avoiding a delay of many seconds in starting up.

2. It may be used to power a remote control receiver, so that when infrared or radio-frequency signals are sent by a remote control device, the equipment is able to respond, typically by changing from standby to fully on mode.

3. Equipment use less power when switched off to power a display, operate a clock, etc.

4. Battery-powered equipment connected to mains electricity can be kept fully charged although switched on; for example, a mobile telephone can be ready to receive calls without depleting its battery charge.

_

Disadvantages of standby power:

The disadvantages of standby power all relate to the energy used. As standby power is reduced, the disadvantages become less. Older devices often used ten watts or more; with the adoption of the One Watt Initiative by many countries, standby energy use is much diminished.

1. Devices on standby consume electricity which must be paid for. The total energy consumed may be of the order of 10% of the electrical energy used by a typical household. The cost of standby energy is easily estimated—each watt of continuous standby consumes about 9kWh of electricity per year, and the price per kWh is shown on electricity bills.

2. Electricity is very often generated by combustion of hydrocarbons (oil, coal, and gas) or other substances, which release substantial amounts of carbon dioxide, implicated in global warming, and other pollutants such as sulphur dioxide, which produces acid rain. Standby power is a significant contributor to electricity usage.

3. As electricity consumption increases, more power stations are needed, with associated capital and running costs.

_

What is no-load power waste?

No-load power waste is a subset of standby power waste. No-load power is the energy used by a device when it is disconnected from its load and performing no function. For example, a mobile phone charger that is plugged into the wall, but not connected to the phone will still consume power. Linear chargers can consume between 0.8 W to 2 W even when they are disconnected from the phone.

_

Is standby power use necessary?

Certain appliance functions do require small amounts of electricity include:

  • Maintaining signal reception capability (for remote control, telephone or network signal)
  • Monitoring temperature or other conditions (such as in a refrigerator)
  • Powering an internal clock
  • Battery charging
  • Continuous display

Good design can make the power requirements for these functions very low (but not yet zero).

_

Bioelectromagnetism:

Bioelectromagnetism (sometimes equated with bioelectricity) refers to the electrical, magnetic or electromagnetic fields produced by living cells, tissues or organisms. Examples include the cell membrane potential and the electric currents that flow in nerves and muscles, as a result of action potentials. Biological cells use bioelectricity to store metabolic energy, to do work or trigger internal changes, and to signal one another. Bioelectromagnetism is studied primarily through the techniques of electrophysiology. Bioelectromagnetism is an aspect of all living things, including all plants and animals. Some animals have acute bioelectric sensors, and others, such as migratory birds, are believed to navigate in part by orienteering with respect to the Earth’s magnetic field. Also, sharks are more sensitive to local interaction in electromagnetic fields than most humans. Other animals, such as the electric eel, are able to generate large electric fields outside their bodies.

_

All living animals emit electrical charges (albeit, most only give off weak ones) during routine muscle movement. However, only a distinct group of (mostly aquatic) animals have a precise sixth-sense that allow them to both detect these electrical charges and (in some cases) physically produce electricity.

_

These are the animals that produce electricity:

  • Electric Catfish
  • Elephant fishes
  • Bonytongues
  • Stargazers
  • Hammerhead Sharks
  • Echidnas
  • Electric Skate
  • Knife fishes
  • Paddle fish
  • Platypus

_

The electric eel is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks of up to 600 volts, which it uses for hunting and self-defense. The electric eel has three abdominal pairs of organs that produce electricity: the main organ, the Hunter’s organ, and the Sach’s organ. These organs make up four-fifths of its body, and are what give the electric eel the ability to generate two types of electric organ discharges (EODs): low voltage and high voltage. These organs are made of electrocytes, lined up so that the current flows through them and produces an electrical charge. When the eel locates its prey, the brain sends a signal through the nervous system to the electric cells. This opens the ion channel, allowing positively-charged sodium to flow through, reversing the charges momentarily. By causing a sudden difference in voltage, it generates a current. The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. In the electric eel, some 5,000 to 6,000 stacked electroplaques are capable of producing a shock at up to 500 volts and 1 ampere of current (500 watts). Such a shock could be deadly for an adult human.

_

Trees give off electricity, scientists say – especially eucalyptus:

Researchers have long believed there is a link between trees and electricity in the atmosphere but have been unable to prove the association. But scientists from the Queensland University of Technology have shown that concentrations of negative and positive ions in the atmosphere were twice as heavy in wooded area as in grassy regions. The charges could be explained by radiation from the gas radon. Radon is a by-product of the radioactive decay of radium, which is exhaled by the ground. Trees acts as pumps, bringing the gas to the surface and releasing it. Because radium is found in rocks and radon is soluble in water, ground water is particularly rich in radon. Trees act as radon pumps, bringing the gas to the surface and releasing it to the atmosphere through transpiration – a process where water absorbed by the root system is evaporated into the atmosphere from leaves. This is especially prevalent for trees with deep root systems, such as eucalyptus.

_

Research on electricity:

_

Magnetic monopoles?

Researchers have discovered a magnetic equivalent to electricity: single magnetic charges that can behave and interact like electrical ones. The work is the first to make use of the magnetic monopoles that exist in special crystals known as spin ice. Writing in Nature journal, a team showed that monopoles gather to form a “magnetic current” like electricity. They showed that when the spin ice was placed in a magnetic field, the monopoles piled up on one side – just like electrons would pile up when placed in an electric field. The phenomenon, dubbed “magnetricity”, could be used in magnetic storage or in computing. In September 2009, two research groups independently reported the existence of monopoles – “particles” which carry an overall magnetic charge. But they exist only in the spin ice crystals. These crystals are made up of pyramids of charged atoms, or ions, arranged in such a way that when cooled to exceptionally low temperatures, the materials show tiny, discrete packets of magnetic charge. Now one of those teams has gone on to show that these “quasi-particles” of magnetic charge can move together, forming a magnetic current just like the electric current formed by moving electrons.

_

The case for sequencing the genome of the electric eel Electrophorus electricus:

A substantial international community of biologists have proposed the electric eel Electrophorus electricus (Teleostei: Gymnotiformes) as an important candidate for genome sequencing. In this study, the authors outline the unique advantages that a genome sequencing project of this species would offer society for developing new ways of producing and storing electricity. Over tens of millions of years, electric fish have evolved an exceptional capacity to generate a weak (millivolt) electric field in the water near their body from specialized muscle-derived electric organs, and simultaneously, to sense changes in this field that occur when it interacts with foreign objects. This electric sense is used both to navigate and orient in murky tropical waters and to communicate with other members of the same species. Some species, such as the electric eel, have also evolved a strong voltage organ as a means of stunning prey. This organism and a handful of others scattered worldwide, convert chemical energy from food directly into workable electric energy and could provide important clues on how this process could be manipulated for human benefit. Electric fishes have been used as models for the study of basic biological and behavioral mechanisms for more than 40 years by a large and growing research community. These fishes represent a rich source of experimental material in the areas of excitable membranes, neurochemistry, cellular differentiation, spinal cord regeneration, animal behavior and the evolution of novel sensory and motor organs. Studies on electric fishes also have tremendous potential as a model for the study of developmental or disease processes, such as muscular dystrophy and spinal cord regeneration. Access to the genome sequence of E. electricus will provide society with a whole new set of molecular tools for understanding the biophysical control of electromotive molecules, excitable membranes and the cellular production of weak and strong electric fields. Understanding the regulation of ion channel genes will be central for efforts to induce the differentiation of electrogenic cells in other tissues and organisms and to control the intrinsic electric behaviors of these cells. Dense genomic sequence information of E. electricus will also help elucidate the genetic basis for the origin and adaptive diversification of a novel vertebrate tissue. The value of existing resources within the community of electric fish research will be greatly enhanced across a broad range of physiological and environmental sciences by having a draft genome sequence of the electric eel.

_

Extracting electricity from water:

Engineers in Canada have discovered a new way to generate electricity. Larry Kostiuk and colleagues at the University of Alberta pumped water through tiny microchannels in a glass disk to directly generate an electrical current (J Yang et al. 2003 J. Micromech. Microeng.13 963). This is the first new way to produce sustainable electricity in 160 years. “It allows for the direct conversion of energy of moving liquid to electricity with no moving parts and no pollution.” When a liquid, like water, comes into contact with a non-conducting solid, the solid surface becomes charged with a thin layer. The dimensions of the microchannels used in the Canadian experiments were comparable with the thickness of this charged layer. This means that if water is then forced through the channel, ions with an opposite charge to the surface preferentially pass through it, and ions with a like charge stay behind. This results in the channel becoming positive at one end and negative at the other – like a battery. If the channel ends are connected together by a wire, current flows. Although the current through an individual channel is very small – about a nanoamp – it can be increased by forcing the water through a large number of parallel channels. Kostiuk and co-workers used a glass disk 2 centimetres in diameter that contained 450000 circular microchannels, each between 10 and 16 microns across. They held a reservoir of water 30 centimetres above the array and allowed it to flow through the disc under hydrostatic pressure, generating a current of 1500 nanoamps in the process. The power output could be improved by increasing the pressure drop, adjusting the size of the microchannels, decreasing the thickness of the glass disk or using a liquid with a higher salt concentration.

_

MIT’s Solar Funnel Concentrates Solar Energy 100 Times:

A group of chemical engineers at MIT have devised a way to collect solar energy 100 times more concentrated than a traditional photovoltaic cell. If their ‘solar funnel’ venture proves to be a success, it could drastically alter how solar energy is collected in the future — there will no longer be a need for massive solar arrays or extensive space to generate significant and sufficient amounts of power. The engineers’ research has determined that carbon nanotubes– hollow tubes made up of carbon atoms — will be the primary instrument in capturing and focusing light energy, allowing for not just smaller, but more powerful solar arrays. Instead of having your whole roof be a photovoltaic cell, you could have little spots that were tiny photovoltaic cells, with antennas that would drive photons into them. The antenna itself is incredibly small – it consists of a fibrous rope about 10 micrometers (millionths of a meter) long and four micrometers thick, containing about 30 million carbon nanotubes. The prototype consisted of a fiber made of two layers of nanotubes, each with different electrical properties. When a photon strikes the surface of the solar funnel, it excites an electron to a higher energy level, which is specific to the material. The relationship between the energized electron and the hole it leaves behind is called an exciton, and the difference in energy levels between the hole and the electron is known as the bandgap. The inner layer of the antenna contains nanotubes with a small bandgap, and nanotubes in the outer layer have a higher bandgap. Excitons like to flow from high to low energy, and in the solar funnel’s case means they can flow from the outer layer to the inner layer where they can exist in a lower energy state. When light strikes the antenna, all of the excitons flow to the center of the antenna where they are concentrated and the photons are converted to an electrical current. Like with all solar cells however, its efficiency depends on the materials utilized for the electrode. In theory, with this new technology, not only could the solar funnels be used to generate power, but they could be used in applications where light needs to be concentrated — such as telescopes or night-vision goggles. The design behind the solar funnel is quite innovative, by capturing the light in a tube (nanotube antenna) boosts the number of photons that can be transformed into energy, but in a similar process to that of tradition solar cells.

_

UCLA Develops Electricity-Generating, Transparent Solar Cell Windows:

A team from UCLA has developed a new transparent solar cell that has the ability to generate electricity while still allowing people to see outside. In short, they’ve created a solar power-generating window! Described as “a new kind of polymer solar cell (PSC)” that produces energy by absorbing mainly infrared light instead of traditional visible light, the photoactive plastic cell is nearly 70% transparent to the human eye—so you can look through it like a traditional window.

_

New Solar Technology Generates Electricity and Hydrogen Gas:

A new solar panel technology includes photovoltaic cells that could generate electricity during the day while at the same time producing hydrogen gas to power a fuel cell at night. The technology that makes this possible is two new types of nanocrystals that replace the traditional organic molecules in a solar panel’s construction. The first nanocrystal is rod-shaped, which allows the charge separation needed to produce hydrogen gas, a reaction known as photocatalysis. The second nanocrystal is composed of stacked layers and generates electricity, thus being photovoltaic. The nanocrystals, which are made of zinc selenide and cadmium sulfide, with a platinum catalyst added, could potentially create a solar panel and fuel cell combination that would provide clean energy 24 hours a day, while also lasting much longer than the typical 20-year lifespan of today’s conventional solar panels.

_

Electricity Production from Wasted Heat:

More than 60 percent of the energy produced by cars, machines, and industry around the world is lost as waste heat — an age-old problem — but researchers have found a new way to make “thermoelectric” materials for use in technology that could potentially save vast amounts of energy. Chemists at Oregon State University have discovered that simple microwave energy can be used to make a very promising group of compounds called “skutterudites,” and lead to greatly improved methods of capturing wasted heat and turning it into useful electricity. Thermoelectric generation of electricity offers a way to recapture some of the enormous amounts of wasted energy lost during industrial activities. Thermoelectric power generation, researchers say, is a way to produce electricity from waste heat — something as basic as the hot exhaust from an automobile, or the wasted heat given off by a whirring machine. OSU researchers have created skutterudites with microwave technology with an indium cobalt antimonite compound, and believe others are possible. They are continuing research, and believe that ultimately a range of different compounds may be needed for different applications of thermoelectric generation.

_

Microbes used to treat human waste might also generate enough electricity to power whole sewage plants, scientists hope:

The technology is based on the relatively new science of electro-microbiology that is finding uses for the discovery that certain microbes can generate an electrical current outside their own cells. In the context of sewage treatment, they would purify waste water by consuming the organic matter in it and use that energy to generate a current that can be harvested and stored. Researchers have described a process in which what they do is use certain micro-organisms which can be connected to devices to generate an electrical current that can be used to generate power. The same technique could see microbes used to generate biofuels, hydrogen gas, methane and other valuable chemicals from the cheap and abundant product of our trips to the bathroom.

_

Wastewater Put To Use Generating Electricity:

The technique developed by OSU, wastewater is treated within a fuel cell. Cleaning bacteria are introduced that oxidize the organic matter, or “dookie,” in sewage and produce electrons. Those electrons travel through the fuel cell, creating an electrical current more powerful than anything seen in prior microbial fuel cells, but without the drawback of producing greenhouse gasses like methane. The technique also has the benefit of being easy to tune to different kinds of wastewater, making it appropriate for not only municipal water treatment plants, but other sources like dairies and food processing facilities, who could not only power their own operations, but conceivably have energy leftover to sell back to the grid. Researchers at Oregon State University have developed a microbial fuel cell that can create 10 to 50, or even 100 times more electricity per volume than similar technologies. After refining the tech for several years using new materials, techniques and altered bacteria, the team can now extract two kilowatts per cubic meter of refuse. As bacteria oxidizes organic matter, electrons — rather than the hydrogen or methane that other methods rely upon — are produced and run from an anode to a cathode within the device to create an electric current.

_

Scientists Generate Electricity From Viruses:

Scientists from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a way to generate power using harmless viruses that convert mechanical energy into electricity. The scientists tested their approach by creating a generator that produces enough current to operate a small liquid-crystal display. It works by tapping a finger on a postage stamp-sized electrode coated with specially engineered viruses. The viruses convert the force of the tap into an electric charge. Their generator is the first to produce electricity by harnessing the piezoelectric properties of a biological material. Piezoelectricity is the accumulation of a charge in a solid in response to mechanical stress. The milestone could lead to tiny devices that harvest electrical energy from the vibrations of everyday tasks such as shutting a door or climbing stairs. It also points to a simpler way to make microelectronic devices. That’s because the viruses arrange themselves into an orderly film that enables the generator to work. Self-assembly is a much sought after goal in the finicky world of nanotechnology.

_

Photosynthesis: A New Source of Electrical Energy? Biofuel Cell Works in Cactus:

Scientists in France have transformed the chemical energy generated by photosynthesis into electrical energy by developing a novel biofuel cell. The advance offers a new strategy to convert solar energy into electrical energy in an environmentally-friendly and renewable manner. The researchers showed that a biofuel cell inserted in a cactus leaf could generate power of 9 μW (microwatt) per cm2. Because this yield was proportional to light intensity, stronger illumination accelerated the production of glucose and O2 (photosynthesis), so more fuel was available to operate the cell. In the future, this system could ultimately form the basis for a new strategy for the environmentally-friendly and renewable transformation of solar energy into electrical energy.

_

Generating Green Electricity from Plants: is it a good idea?

In a new desperate attempt to produce renewable energy from natural non-emission sources, a team of researchers at the Massachusetts Institute of Technology was able to produce electricity from the broad leaf Maple trees. The energy produced with trees is within the Millivolt range (1/1000 of a volt), which is not a big deal. What the team considers an achievement is that they were able to store energy from trees and then use it to run small electronic devices.

_

Green plants are known to be able to harvest the energy from the sunlight and transform that energy into food and oxygen. This process is known as photosynthesis. In photosynthesis the photons (units of light energy) from the sun hit certain molecules inside the chloroplasts (the small green organelles inside the plant cell that carry out photosynthesis) causing the emission of an electron.This electron moves from one molecule to another through a series of cytochromes (certain types of proteins) called photosystems I and II. While the electron is moving it is losing the energy it acquired from the photon (from the sun light) and this energy is transformed into two chemical forms of energy (NADPH2 and ATP). And finally the electron is used to help split the water molecule which is the first step on releasing oxygen to the atmosphere. The rest of the photosynthesis process is a series of chemical reactions through which carbon dioxide is fixed into organic material (glucose).The summary of this process is the consumption of carbon dioxide and water, facilitated by energy from the sun, to produce glucose and oxygen.

_

Plants produce this electric current in order to perform the photosynthesis necessary to produce its own (and our) food, and to help clean up the environment from carbon dioxide which is causing global warming with the greenhouse effect. When we take some of this electricity we are reducing the efficiency of the photosynthesis process. The result will be less food and more carbon dioxide. So generating green electricity from plants is not a good idea.

_

Scientists attempt to utilize rice plants to generate electricity:

In a recent Environmental Science & Technology article, a team of scientists describes a method that takes advantage of a process called rhizodeposition to capture some of the energy produced in rice paddies, possibly before it gets released in the form of methane. Rhizodeposition is a natural process where plants transfer organic material through their roots to the soil. Rhizodeposition releases exudates and root residues, which decompose to produce methane. It is possible to reduce methane emissions by using rhizodeposits, the organic material produced by rhizodeposition, to generate electricity via sediment microbial fuel cells (SMFC). In the SMFC design, the anode is submerged in the soil where the plant is rooted and a cathode is placed in the overlying water. Microbially catalyzed oxidation of rhizodeposits delivers electrons to the anode. The electrons then travel through an electrical circuit that contains a power user and then back to the cathode. Upon reaching the cathode, the electrons react with the available oxygen. The researchers propose that this process can derive power from living rice plants. Over the course of two years, they tested the performance of SMFCs in rice paddies. They discovered that, by using SMFCs, the oxidation of rhizodeposits does produce electrical power in a sustainable way. The highest sustained electrical output was 330 W per hectare of growing area.The SMFCs have a coulometric efficiency of 31 percent and an energetic efficiency of 9 percent.

_

A new system combines the power of plants and photovoltaics to make solar power cheap and durable:

When plants engage in photosynthesis, sunlight breaks apart water and CO2 to release oxygen and build plant—and people—food. It’s cheap and ubiquitous but not much use for powering a home. Photovoltaic devices use semiconducting material like silicon in a related way, with incoming photons knocking loose electrons to generate electricity. Such devices can produce a lot of electricity on a bright sunny day. Unfortunately, they’re too expensive for most folks to afford. But what if you combined the two? That’s exactly what an international consortium of scientists have done, creating a truly green solar cell—and one that can be made from something as common as grass clippings. The findings are in the issue of Nature: Scientific Reports. This “electric nanoforest” only produces a trickle of electricity at present, but with refinement it could begin to produce useful amounts of current. Plus, the raw materials are durable and cheap: any living green vegetation will do—nature has seen to that. If such devices can be improved substantially enough, plant-based photovoltaics may finally bring affordable solar power to the remote villages where it’s needed most.

__

How would life be with no electricity?


__

Life comes to a standstill without electricity in cities and towns. In cities, modern household gadgets like washing machine, refrigerator, home theater system, air conditioner, kitchen appliances like oven, hand blender, mixer, drinking water purifier; official gadgets like computers, printers, scanners, internet devices run on electricity. Mobiles phones, digital cameras, iPods and laptops are integral parts of our city lifestyle. Batteries of phones, laptops, cameras need to be charged with electricity from time to time. Cell phone and Internet are two major mediums of communication in the present time. If supply of electricity is cut off for a few hours, communication is disrupted slowing the pace of life in cities. There would be no telephone or electrical poles, nothing would be digital. We wouldn’t have much of our scientific equipment, no pumping or drilling equipment, one would only have ice in the winter because there would be no refrigeration. Most of our medical equipment wouldn’t exist. Man would only be able to work during daylight hours. Many of the things we take for granted today would never have been invented without electricity. Much of our production would still be done by hand because the factories that manufacture items wouldn’t have assembly lines as they do today. The picture of life without electricity in villages is not as grim as in cities. However, the necessity of electricity is undeniable in some fields of rural life. For example, water pumps which run on electricity are used to irrigate agricultural fields. In a small town Daman where I live, water comes in my home from bore well using electric pump. Without electricity, there would be no water in my home. Evidently life depends on electricity as we depend on gadgets, appliances and electric motors and they depend on electricity for functioning. To say it brief, life with no electricity is a nightmare.

_

Establishment of Non-Electric life style:

Yasuyuki Fujimura, a doctor of engineering and an inventor in Japan, has been advocating a “non-electric” life style that intentionally avoids the use of electricity. The phrase “non-electric” may sound a little unfamiliar, but it is different from “anti-electrification” that condemns electricity on principle. The phrase is meant to communicate the idea that it should be possible to live happily and richly while enjoying a moderate level of comfort and convenience without depending on electricity. There are many interesting home appliances that can be operated without electric power. One example is a non-electric refrigerator. It uses a phenomenon called radiational cooling together with the natural convection currents of water. Radiational cooling occurs when infrared radiation is emitted from an object’s surface, causing its temperature to decrease. On a clear night, infrared rays are emitted from the ground into the atmosphere, cooling the air down. This is why the night is extremely cold in the desert. Most people have experienced water’s natural convection currents when warm water rises while cold water sinks and pools at the lowest level. The cooling unit of the refrigerator (capacity 200 litres) is made of metal that has high thermal conductivity. A large volume of water (about 250 litres) is stored around this unit as a coolant. Radiator panels are placed on top so that the inner surface of the panel touches the coolant water. The heat of things stored in the cooling unit is conveyed to the surrounding water by the metal, and the heat goes up by natural convection. Thus it is conveyed to the radiator panel, and emitted through radiational cooling. A non-electric composting toilet uses the power of microorganisms, which can decompose human waste into manure without an electric pump. So this engineer has devised various methods right from making a cup of coffee to refrigerator to toilet in order to live non-electric life style.

_

_

My theory of electromagnetism:

Traditional scientific teaching suggest that static electrical charge has electric field and moving electrical charge (additionally) has magnetic field. Current generate magnetic field. Voltage is due to imbalance of charges and current is due to flow of charges. Voltage is related to electric field and current is related to magnetic field. Electricity and magnetism are intimately related but still different entities. Changing magnetic field generates electric field and changing electric field generates magnetic field. Special theory of relativity tries to visualize electric field and magnetic field as similar field with reference to the motion of an observer. When electricity flows in a wire, there is movement of charges which is independent of movement of electrical energy (electromagnetic waves) even though the charges (electrons) provide a medium to transmit electrical energy.

_

When +ve and –ve charges are separated by any means creating net imbalance of charges, voltage is generated no matter whether the charges are static or in motion. Static charges would have electric field and moving charges would have electromagnetic (electric + magnetic) field. When +ve and/or –ve charges move in a medium (conductor), current is generated. Voltage can cause current when the medium (conductor) has low resistance (free charges).Voltage cannot cause current when the medium is insulator (no free charges). When voltage does cause current, electrical energy flow as electromagnetic waves. Even in superconductor (zero resistance) where current is flowing without voltage, some voltage is required to initiate current in the first place. In my view, voltage is the basis of electromagnetic force and current is only sequel of voltage in a medium. Changing magnetic field generate voltage in a medium as energy of changing magnetic field realign charges in a medium to cause imbalance of charges resulting in voltage which induces current in a coil in a generator. When voltage causes charges to move in a wire, the magnetic fields of individual charges get aligned to generate magnetic field around electric wire which moves compass. So called magnetism created by current is nothing but alignment of magnetic field of electrical charges flowing in a conductor under push of voltage. The magnetic field strength B within a normal wire carrying current increases linearly with distance from the centre of the wire, and reaches a maximum value at the surface of the wire. Within a superconductor, however, the magnetic field B is zero because there is current without voltage. When the same superconductor becomes normal conductor with current and voltage, the same magnetic field B returns.

_

In electric motor, voltage across electric coil generates current resulting in propagation of electromagnetic waves and due to shape of coil, magnetic field get strengthened to produce electromagnet. This magnetic field of electromagnet is result of alignment of magnetic field of moving individual electrons under influence of voltage. So voltage is the basis of electricity, electrical energy and electromagnetism. Since flow of charge is directly proportional to voltage and inversely proportional to resistance, with resistance remaining constant in copper wire, greater voltage will generate greater magnetic field. In superconductor electromagnet, great charges flow as even though voltage is low, the resistance is near zero. So superconductor electromagnet is very strong.

_

Remember, whenever the word field is used, gravitational-electric-magnetic; basically field is invisible energy. There is nothing like magnetism. It is a play of words. It is all electricism—the electric field of the stationary charge is electric field A and additionally, the charge acquires electric field B when in motion. The so called magnetic fields are electrical fields B of moving charge. When separation of +ve and –ve charges occur, imbalance in electrical fields generates voltage. Electron is never stationary and hence has both electric fields A plus B. That is why when electron is accelerated, it emit photons. Photon is nothing but self propagating electrical field A & B without mass and charge. Charge cannot exist without mass. Mass can exist without charge. Mass can be converted into energy and vice versa. Charge cannot be converted into energy. Charge can carry or transmit or transfer energy. When voltage is applied (EMF) across a conductor, it pushes the charge (electrons in copper wire) resulting in its acceleration, resulting in release of photons which is nothing but electrical energy that flows from source to load. The photon emitted by accelerating electron is having frequency of 50/60 Hz in AC circuit which is very low energy photon which cannot penetrate through the interior of the copper wire. However, there is Electron Sea of billions of billions of electrons which emit billions of billions of photons. The photon emitted in the interior of wire will hit another electron and accelerate it which in turn emits another photon and the process continues instantly till photons starts flowing along copper wire on the exterior of the wire. In order to generate constant rate of photons, constant voltage is to be applied to electrons to maintain acceleration. The charges merely transfer energy of voltage-push into photons. When the voltage generate current in a wire, it generate EM wave (photons) as electrical energy being transferred from source to load. So both electrical current and electrical energy (photons) are consequences of voltage across a conductor. The same voltage cannot generate current in insulator (no free electrons) and hence no electrical energy flows in it. Remember, electrons are not the only source of electric current. When any electrical charge (proton or any ion) is accelerated in any medium under influence of voltage, electrical current and electrical energy (photons) flows. It is the acceleration of electric charge under influence of voltage that emits photons. In fact, any energy field which can affect the motion of charge particle can cause release of photons. In MRI machines, varying electromagnetic field causes change in the spin of a proton and as that proton returns to baseline spin, a photon is emitted by that proton. So not only electron but any charges particle emits photon when its motion is accelerated under influence of energy field.

_

When electron and positron meet, photons are created, mass is lost and charge is annihilated. You cannot destroy an electron alone with its charge and convert it in energy-photon since photon has no charge. So when electron is destroyed and converted into energy, its negative charge is lost along with positive charge of a proton which then becomes neutron. Positive and negative charges are destroyed together or created together. You cannot create a single positive or negative charge (read my theory of “Duality of Existence”).

_

Since electric field A is a property of a static charge and electric field B is a property of a moving charge (moving charge has both A plus B fields), both fields A and B are different and their planes are perpendicular to each other. The alignment of B fields causes magnetism. Magnetic dipole has on one end electric B fields emitting and on other end electric B field ingoing. Emitting B fields repel each other but emitting and ingoing B field attract each other. By convention, we call emitting electric B fields as North Pole and ingoing electric B fields as South Pole. If electric A fields were to be aligned, we would have neo-magnet with West pole and East pole.

_

The moral of the story:

_

1. Electricity is transfer of electrical energy as electromagnetic waves from source to load using motion of charged particles (electrons in copper wire) as source of photons under influence of voltage. The direction & speed of electrical energy (photons) is independent of direction & speed of motion of charges.

_

2. Electricity in your home is transfer of electrical energy as electromagnetic waves outside copper wires from source to load (appliance) generated by oscillation or vibration (movement) of electrons in the copper wire. This is AC circuit. Electricity in appliances like computer is DC circuit transmitting the same electrical energy as electromagnetic waves outside wires of circuit generated by movement of electrons from negative terminal to positive terminal. AC current means acceleration and deceleration of Electron Sea alternately in opposite directions under influence of alternating voltage. DC current means acceleration of Electron Sea from negative terminal to positive terminal under influence of steady voltage. The only difference between photons of AC power and DC power is the frequency; AC power photons have frequency of 50/60 Hz while DC power photons have zero frequency. Higher the frequency, the more rapidly field varies. Zero frequency means fields do not vary. That is why your computer has an adapter converting AC into DC power.

_

3. Electricity is confusion between language and science. In DC electrical circuit, current moves from +ve terminal to –ve terminal by convention and electrons move from –ve terminal to +ve terminal. Current is defined as flow of electrical charge (electrons in copper wire) but direction of current is opposite direction of flow of charges. There is lot of confusion about neutral wire and ground wire in AC mains electricity in your home especially when neutral wire is grounded at transformer level or at generator level.

_

4. Voltage difference between two points is equal to the work (in joules) which would have to be done per unit charge (in coulombs) to move the charge between these two points and it is the acceleration of these charges under influence of voltage that releases photons (electrical energy).

_

5. The coulomb is defined as the quantity of charge that has passed through the cross section of an electrical conductor carrying one ampere current within one second. That means 6.242×1018 electrons are moving in a wire every second i.e. one coulomb negative charge as electrons are negatively charged.

_

6. More than 80% of our electricity comes from combustion of fossil fuels (coal, natural gas and oil) and nuclear fission that the environmentalists despise. We have a long way to go to get no carbon and non-nuclear electricity.

_

7. Water footprint for electricity generation translates into an average of 95 Liters of water to produce 1 kilowatt-hour of electricity. Natural gas yields the most energy per unit volume of water consumed compared to coal and nuclear power.

_

8. Electricity accounts for 40% of global energy-related CO2 emissions as combustion of fossil fuel is a major source of electricity; these emissions will grow by 58% globally by 2030.  Natural gas creates significantly smaller environmental impacts than coal.

_

9. On average, the harm produced by burning the coal is over twice as high as the market price of the electricity.

_

10. Modern gas-fired power plants are much cleaner and more efficient than their predecessors. They are also larger, cheaper to build, less noisy, less polluting, and easier to switch on and off. On a full cost (including fuel as well as capital depreciation costs) basis, gas is more expensive than existing nuclear power generation, but significantly cheaper than coal or renewable power. If environmental costs are added to this analysis, the advantages of gas will be greater.

_

11. If any country converted to CFL technologies instead of incandescent light bulbs (ordinary light bulb), the electricity consumed to produce light could be reduced by up to 70 percent! Replacing all inefficient lighting with CFLs would save 409 terawatt hours (TWh) per year worldwide, 2.5% of the world’s electricity consumption. Exchanging incandescent light bulb for efficient CFLs on a global scale would achieve annual CO2 reductions of 230 million tons.

_

12. It is estimated by International Energy Agency that 5 to 15% of household electricity consumption worldwide is wasted in standby mode.

_

13. Electricity is an evidence of fallibility of human intelligence. Due to inefficiency in electrical generation, transmission and use, most of energy is lost. For example, out of 1000 joules of energy utilized for electricity generation, 60 % energy is lost in heat so that only 400 joules of energy available for transmission. Then, 7 to 10 % energy is lost in transmission of electricity so that out of 400 joules, only 360 joules reach your home. (In a country like India, transmission loss and theft amount to 40 % loss of energy) Then, 10 % energy is lost in standby mode so that only about 320 joules of energy available to consumer for actual use. Then, incandescent light bulb waste 98 % energy as heat and only rest is available as light in your home. So out of 320 joules, 313 joules are wasted as heat by light bulb and only 7 joules of energy is converted into light to illuminate your home. In other words, out of 1000 joules of energy consumed, only 7 joules used for lighting purpose and rest 993 joules are lost. What is the point of scientific and technological development? The least we can do is to phase out incandescent light bulb and replace it with CFL. I am sure we can do more. That means more efficient electricity production, transmission and use. I have not discussed waste of electricity by consumers themselves.

_

14. My theory of electromagnetism asserts that there is nothing like independent magnetism. It is electricism all the way. There are two types of electric fields, electric field A in static charge and additionally electric field B in moving charge. Electron is never stationary and hence has both electric fields A plus B. That is why when electron is accelerated, it emit photons. Photon is nothing but self propagating electric field A and B without mass and charge. Charge cannot exist without mass. Mass can exist without charge. Mass can be converted into energy and vice versa. Charge cannot be converted into energy. Charge can carry or transmit or transfer energy. Voltage across a medium causes electrical charges in that medium to flow resulting in acceleration of charges, resulting in emission of photons (electrical energy). The charges merely transfer energy of voltage-push into photons. The alignment of electric B fields causes magnetism. Magnetic dipole has on one end electric B fields emitting and on other end electric B field ingoing. Emitting B fields repel each other but emitting and ingoing B field attract each other. By convention, we call emitting electric B fields as North Pole and ingoing electric B fields as South Pole. If electric A fields were to be aligned, we would have neo-magnet with West pole and East pole.

_

Dr. Rajiv Desai. MD.

September 4, 2012

_

Postscript:

Please do read my articles on “The Energy”, “Nano World” and “Duality of Existence” along with this article on “Electricity” as they are complementary. I welcome scientists and electrical engineers to assess this article. Their criticism and suggestions may be communicated to me through my email ID: [email protected] 

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

1,618 comments on “ELECTRICITY”

Leave a Reply

Your email address will not be published. Required fields are marked *

Designed by @fraz699.