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Electricity

ELECTRICITY

Electricity has been known since ancient times, but scientists could not make use of it safely until the eighteenth century. Thomas Edison's invention of the electric lightbulb in 1879 sparked the demand for electric power that continues to this day, ultimately resulting in the need for legislative and regulatory controls on the electric-power-generating industry.

History

By the end of the nineteenth century, the United States had completed its transition from using wood as a major energy source to using coal, and the next transition from coal to oil and natural gas was just beginning. By the early twentieth century, both homes and businesses increased their demand for electric power, and electric utilities obtained long-term franchises from municipalities.

In 1920, the Federal Power Act (FPA), 16 U.S.C.A. §§ 791a–828c, was passed in response to increased competition between electric utilities and a lack of consistent service to rural areas. The Federal Power Act gave the Federal Power Commission the authority to license hydroelectric plants. Later, President franklin d. roosevelt encouraged Congress to create part II of the act, which gave the Federal Power Commission the power to regulate the transmission of electric energy (16 U.S.C.A. §§ 824–824m). This legislation was necessary to guard against potential abuses of the utility companies' monopolistic structure and to ensure adequate and consistent service nationwide.

As more and larger electric generating plants were constructed and as more electric power lines were strung, legislators believed that through economies of scale, electric utility monopolies could actually offer lower costs to consumers than could competition between smaller utilities. Because of the capital-intensive nature of providing electric power, and the sunken costs of building plants and stringing lines, it is more cost-effective to spread these costs over the large and consistent customer base provided by a monopoly.

Structure of the Industry

Modern electric utilities have three major organizational components: generation (power plants), transmission (high-voltage bulk power between utilities), and distribution (low-voltage power to ultimate consumers). Modern electric utilities not only produce the power they need for their consumers but also pool and coordinate excess electricity with other utilities.

In 2001, the United States had the ability to produce over 788 million megawatts of electrical energy. Pooling and coordination of electrical energy take place through high-voltage wires that are maintained and referred to as the national grid; high-voltage wires are used because they allow transmission at a lower current, which generates less heat and results in less energy loss. At regional distribution centers closer to the ultimate consumers, the electrical energy is transformed into the low-voltage, higher-current electricity delivered to homes and businesses.

Major electric utilities produce electric power by burning coal, harnessing the hydroelectric energy produced by dams, and initiating and maintaining nuclear fission. Smaller, independent power producers use hydroelectric energy in addition to wood energy, geothermal energy, and biomass, which are all forms of renewable energy. Nuclear electric generating plants were constructed after the passage of the Atomic Energy Act (42 U.S.C.A. § 2011), which removed the government's monopoly over nuclear power, in 1946, and the Price-Anderson Act (42 U.S.C.A. § 2210), which allowed for private ownership of uranium, in 1957.

Commercial nuclear energy expanded in the 1960s and the early 1970s, and most consumers welcomed what was thought to be a safe and inexpensive source of energy. From the late 1970s to the 1990s, the dangers of nuclear energy and the expense of environmental contamination and lack of safe waste storage contributed to the end of nuclear power plant construction. No U.S. nuclear power plants have been ordered since 1978. Coal and hydroelectric energy continue to be the principal sources of commercial electric power.

Modern Legislation and Regulation of the Industry

The generation, transmission, and distribution of electric power are heavily regulated. At the federal level, the transmission of electric power between utilities is governed by the public utilities Regulatory Policies Act (PURPA) (Pub. L. No. 95-617 [codified in various sections of U.S.C.A. tits. 15, 16]). In PURPA, Congress gave the Federal Energy Regulatory Commission (FERC) jurisdiction over energy transmission. PURPA requires that independent power producers (IPPs) be allowed to interconnect with the distribution and transmission grids of major electric utilities. In addition, PURPA protects IPPs from paying burdensome rates for purchasing backup power from major utilities, and sets the rate at which the utilities can purchase power from IPPs at the major utilities' "avoided cost" (market cost minus the production costs "avoided" by purchasing from another utility) of producing the power.

The primary regulation of the generation, distribution, and transmission of electric power occurs at the state level through various state public utility commissions. Because the production of electric energy is connected with a public interest, states have a vested interest in overseeing it and working to guarantee that electricity will be produced in a safe, efficient, and expedient manner. In exchange for a monopoly in a particular geographic region, an electric utility must agree to supply electricity continuously and has a duty to avert unreasonable risks to its consumers. Electric utility companies must provide electricity at applicable lawful rates, and must file rate schedules with the public service commissions. Sometimes these rates are challenged, and administrative hearings are held to allow the utilities to petition for rate increases. Electricity rates must be high enough to cover the cost of production and must allow a fair return on the current value of capital investment. Rates that would allow significantly more than a fair return may be struck down as unreasonably high.

The regulatory landscape began to change in the late 1990s, as FERC endorsed the concept of greater competition in the sale of electricity. Advocates of competition contended that the production and delivery of electricity were two distinct activities that should not be bundled into one charge for energy consumer. Instead, they argued for a free market system where electricity could be bought and sold at the wholesale level for the lowest price and then delivered anywhere in the country. National energy producers and wholesalers sought to end the dominance of state and regional utility companies, which controlled the power lines through which these new competitors wanted to transmit electricity.

FERC issued an order in 1996 that opened up the electrical transmission lines owned by state power utilities to other wholesalers of electricity. The order required that utility companies break out their wholesale electricity rates to show how much was being charged for the generation of power, the transmission of electricity, and other ancillary services. In addition, whatever these companies charged to transmit their own electricity was the maximum amount they could charge other companies that wanted to use their transmission lines.

These regulations were also extended to the retail transmission of electricity in interstate commerce. However, FERC rejected the calls of energy resellers (such as the Texas-based Enron Corporation) to permit this same type of open access to retail power sales. This would have meant that consumers and businesses could obtain their power from an out-of-state provider, much like they can choose their long-distance telephone provider. FERC rejected this approach because it feared that it would be costly and difficult to administer.

The order led some states to deregulate their utilities to permit competition in this new legal environment. However, New York and eight other states objected to the order, believing it usurped state authority. They filed suit in federal court challenging the legality of the order. Enron also filed suit, challenging FERC's denial of access to the retail transmission of electricity. The two lawsuits were consolidated and heard by the Circuit Court of Appeals for the District of Columbia. The appellate court rejected the arguments of the states and Enron, concluding that FERC had authority under the FPA to issue such an order.

The Supreme Court, in New York v. Federal Energy Regulatory Commission, 535 U.S. 1, 122 S.Ct. 1012, 152 L.Ed.2d 47 (2002), upheld the circuit court decision. The Court concluded that although the states had regulated electricity for 60 years, this did not mean they had the underlying authority to make such decisions. The federal government had merely allowed these practices to continue. FERC had the authority to issue the order and had exercised this power lawfully. Though FERC had the authority to allow Enron and other companies to enter the retail sales market, the Court held that FERC had acted within its administrative powers in declining to exercise its jurisdiction at this time. FERC's decision not to claim jurisdiction over the retail market could be changed in the future.

The likelihood of FERC changing its mind anytime soon seemed unlikely. In 2001, the state of California was in the midst of an electricity crisis. A shortage of electricity led to skyrocketing prices, blackouts and brownouts, and expensive long-term contracts by the state to secure a supply of electricity into the future. The price of electricity jumped from $30 per megawatt hour to $361 per megawatt hour. However, within months, allegations surfaced that wholesalers such as Enron had manipulated the market to create artificial shortages, which led to the sale of electricity at inflated prices. A FERC administrative judge ruled in November 2002 that rates in California had been too high and that the state should receive a $1.8 billion refund. This was considerably less than the $8.9 billion refund the state sought.

Dangers and Liabilities

Electricity, especially at high voltages or high currents, is a dangerous commodity. Faulty wiring, power lines that are close to trees and buildings, and inadequate warning signs and fences around transformer stations and over buried electrical cables can subject an individual to electric shock or even electrocution. Because of the ultrahazardous nature of providing electric power, states have many statutes and regulations in place to protect the public from electric shock.

Other dangers from electricity include stray voltage and electromagnetic field radiation. Stray voltage affects farm animals, especially dairy cattle. On dairy farms, it occurs when cattle drink from electric feeding troughs or are attached to electric milking machines, and small electric shocks pass through the cattle, through their hooves, and into the ground. Repeated shocks can inhibit or destroy the milk-producing capability of dairy cattle. Liability for stray voltage on farms can be attributed to public utilities when wiring is faulty or negligently connected to a farmer's equipment. Some juries have awarded thousands of dollars to farmers whose cattle have been damaged by this phenomenon.

Electromagnetic fields are created whenever current moves through power lines. The strength of these fields drops off exponentially as the distance from the power lines increases. Individuals whose homes or businesses are close to power wires must live and work in these fields. Some individuals who live or work near high-voltage power lines have developed brain cancer and leukemia, and blame their condition on the constant exposure to electromagnetic field radiation. Studies have shown a correlation between electromagnetic fields and cancer, but many of the studies have been challenged as methodologically flawed. By the mid-1990s, no conclusive scientific evidence proved an epidemiological relationship between cancer and the electromagnetic fields produced by highvoltage power lines.

further readings

Atterbury, Mark S. 1995."The Strict Liability of Power Companies for Cancer Caused by Electromagnetic Fields." Southern Illinois University Law Journal 19.

Federal Energy Regulatory Commission. Available online at <www.ferc.gov> (accessed June 4, 2003).

Handmaker, Robert S. 1989."Deregulating the Transmission of Electricity: Wheeling Under PURPA Sections 203, 204 and 205." Washington University Law Journal 67.

Hunt, Sally. 2002. Making Competition Work in Electricity. New York: John Wiley.

Laitos, Jan G., and Joseph P. Tomain. 1992. Energy and Natural Resources Law. St. Paul, Minn.: West.

Sweeny, James. L. 2002. The California Electricity Crisis. Palo Alto, Calif.: Hoover Institution.

Yelkovac, Peter G. 1994. "Homogenizing the Law of Stray Voltage: An Electrifying Attempt to Corral the Controversy." Valparaiso University Law Review 28.

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electricity

electricity, class of phenomena arising from the existence of charge. The basic unit of charge is that on the proton or electron—the proton's charge is designated as positive while the electron's is negative. There are three basic systems of units used to measure electrical quantities, the most common being the one in which the ampere is the unit of current, the coulomb is the unit of charge, the volt is the unit of electromotive force, and the ohm is the unit of resistance, reactance, or impedance (see electric and magnetic units).

Properties of Electric Charges

According to modern theory, most elementary particles of matter possess charge, either positive or negative. Two particles with like charges, both positive or both negative, repel each other, while two particles with unlike charges are attracted (see Coulomb's law). The electric force between two charged particles is much greater than the gravitational force between the particles. The negatively charged electrons in an atom are held near the nucleus because of their attraction for the positively charged protons in the nucleus.

If the numbers of electrons and protons are equal, the atom is electrically neutral; if there is an excess of electrons, it is a negative ion; and if there is a deficiency of electrons, it is a positive ion. Under various circumstances, the number of electrons associated with a given atom may change; chemical bonding results from such changes, with electrons being shared by more than one atom in covalent bonds or being transferred from one atom to another in ionic bonds (see chemical bond). Thus many of the bulk properties of matter ultimately are due to the electric forces among the particles of which the substance is composed. Materials differ in their ability to allow charge to flow through them (see conduction; insulation); materials that allow charge to pass easily are called conductors, while those that do not are called insulators, or dielectrics. A third class of materials, called semiconductors, conduct charge under some conditions but not under others.

Properties of Charges at Rest

Electrostatics is the study of charges, or charged bodies, at rest. When positive or negative charge builds up in fixed positions on objects, certain phenomena can be observed that are collectively referred to as static electricity. The charge can be built up by rubbing certain objects together, such as silk and glass or rubber and fur; the friction between the objects causes electrons to be transferred from one to the other—from a glass rod to a silk cloth or from fur to a rubber rod—with the result that the object that has lost the electrons has a positive charge and the object that has gained them has an equal negative charge. An electrically neutral object can be charged by bringing it in contact with a charged object: if the charged object is positive, the neutral object gains a positive charge when some of its electrons are attracted onto the positive object; if the charged object is negative, the neutral object gains a negative charge when some electrons are attracted onto it from the negative object.

A neutral conductor may be charged by induction using the following procedure. A charged object is placed near but not in contact with the conductor. If the object is positively charged, electrons in the conductor are drawn to the side of the conductor near the object. If the object is negatively charged, electrons are drawn to the side of the conductor away from the object. If the conductor is then connected to a reservoir of electrons, such as the ground, electrons will flow onto or off of the conductor with the result that it acquires a charge opposite to that of the charged object brought near it.

See also pole, in electricity and magnetism.

Properties of Charges in Motion

Electrodynamics is the study of charges in motion. A flow of electric charge constitutes an electric current. Historically, the direction of current was described in terms of the motion of imaginary positive charges; this convention is still used by many scientists, although it is directly opposite to the direction of electron flow, which is now known to be the basis of electric current in solids. Current considered to be composed of imaginary positive charges is often called conventional current. In order for a current to exist in a conductor, there must be an electromotive force (emf), or potential difference, between the conductor's ends. An electric cell, a battery of cells, and a generator are all sources of electromotive force; any such source with an external conductor connected from one of the source's two terminals to the other constitutes an electric circuit. If the source is a battery, the current is in one direction only and is called direct current (DC). If the source is a generator without a commutator, the current direction reverses twice during each rotation of the armature, passing first in one direction and then in the other; such current is called alternating current (AC). The number of times alternating current makes a double reversal of direction each second is called the frequency of the current; the frequency of ordinary household current in the U.S. is 60 cycles per sec (60 Hz), and electric devices must be designed to operate at this frequency.

In a solid the current consists not of a few electrons moving rapidly but of many electrons moving slowly; although this drift of electrons is slow, the impulse that causes it when the circuit is completed moves through the circuit at nearly the speed of light. The movement of electrons in a current is not steady; each electron moves in a series of stops and starts. In a direct current, the electrons are spread evenly through the conductor; in an alternating current, the electrons tend to congregate along the surface of the conductor. In liquids and gases, the current carriers are not only electrons but also positive and negative ions.

History of Electricity

From the writings of Thales of Miletus it appears that Westerners knew as long ago as 600 BC that amber becomes charged by rubbing. There was little real progress until the English scientist William Gilbert in 1600 described the electrification of many substances and coined the term electricity from the Greek word for amber. As a result, Gilbert is called the father of modern electricity. In 1660 Otto von Guericke invented a crude machine for producing static electricity. It was a ball of sulfur, rotated by a crank with one hand and rubbed with the other. Successors, such as Francis Hauksbee, made improvements that provided experimenters with a ready source of static electricity. Today's highly developed descendant of these early machines is the Van de Graaf generator, which is sometimes used as a particle accelerator. Robert Boyle realized that attraction and repulsion were mutual and that electric force was transmitted through a vacuum (c.1675). Stephen Gray distinguished between conductors and nonconductors (1729). C. F. Du Fay recognized two kinds of electricity, which Benjamin Franklin and Ebenezer Kinnersley of Philadelphia later named positive and negative.

The Leyden Jar and the Quantitative Era

Progress quickened after the Leyden jar was invented in 1745 by Pieter van Musschenbroek. The Leyden jar stored static electricity, which could be discharged all at once. In 1747 William Watson discharged a Leyden jar through a circuit, and comprehension of the current and circuit started a new field of experimentation. Henry Cavendish, by measuring the conductivity of materials (he compared the simultaneous shocks he received by discharging Leyden jars through the materials), and Charles A. Coulomb, by expressing mathematically the attraction of electrified bodies, began the quantitative study of electricity.

A new interest in current began with the invention of the battery. Luigi Galvani had noticed (1786) that a discharge of static electricity made a frog's leg jerk. Consequent experimentation produced what was a simple electron cell using the fluids of the leg as an electrolyte and the muscle as a circuit and indicator. Galvani thought the leg supplied electricity, but Alessandro Volta thought otherwise, and he built the voltaic pile, an early type of battery, as proof. Continuous current from batteries smoothed the way for the discovery of G. S. Ohm's law (pub. 1827), relating current, voltage (electromotive force), and resistance (see Ohm's law), and of J. P. Joule's law of electrical heating (pub. 1841). Ohm's law and the rules discovered later by G. R. Kirchhoff regarding the sum of the currents and the sum of the voltages in a circuit (see Kirchhoff's laws) are the basic means of making circuit calculations.

Era of Electromagnetism

In 1819 Hans Christian Oersted discovered that a magnetic field surrounds a current-carrying wire. Within two years André Marie Ampère had put several electromagnetic laws into mathematical form, D. F. Arago had invented the electromagnet, and Michael Faraday had devised a crude form of electric motor. Practical application of a motor had to wait 10 years, however, until Faraday (and earlier, independently, Joseph Henry) invented the electric generator with which to power the motor. A year after Faraday's laboratory approximation of the generator, Hippolyte Pixii constructed a hand-driven model. From then on engineers took over from the scientists, and a slow development followed; the first power stations were built 50 years later (see power, electric).

In 1873 James Clerk Maxwell had started a different path of development with equations that described the electromagnetic field, and he predicted the existence of electromagnetic waves traveling with the speed of light. Heinrich R. Hertz confirmed this prediction experimentally, and Marconi first made use of these waves in developing radio (1895). John Ambrose Fleming invented (1904) the diode rectifier vacuum tube as a detector for the Marconi radio. Three years later Lee De Forest made the diode into an amplifier by adding a third electrode, and electronics had begun. Theoretical understanding became more complete in 1897 with the discovery of the electron by J. J. Thomson. In 1910–11 Ernest R. Rutherford and his assistants learned the distribution of charge within the atom. Robert Millikan measured the charge on a single electron by 1913.

Bibliography

See D. L. Anderson, Discovery of the Electron: The Development of the Atomic Concept of Electricity (1964); W. T. Scott, The Physics of Electricity and Magnetism (2d ed. 1966); M. Kaufman and J. A. Wilson, Basic Electricity (1973); E. T. Whittaker, History of Theories of Aether and Electricity (1954, repr. 1987).

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Electricity

Electricity

Electricity is a form of energy caused by the presence of electrical charges in matter. All matter consists of atoms, and atoms themselves contain charged particles. Each proton in an atomic nucleus carries one unit of positive electric charge, and each electron circling a nucleus carries one unit of negative electric charge. Electrical phenomena occur when electrons escape from atoms. The loss of one or more electrons (negative charges) from an atom leaves behind a positively charged fragment known as a positive ion. An electric current is produced when a mass of electrons released from atoms begins to flow.

Static and current electricity

Electrical phenomena can be classified in one of two general categories: static electricity or current electricity. The term static electricity refers to the behavior of electrical charges at rest. Suppose you hang two ping-pong balls from silk threads so that they are about 2 inches (5 centimeters) apart. Then imagine that each ball is rubbed with a piece of wool. The two balls become electrically charged with the same sign. Because like charges repel each other, the two balls will swing away from each other because of the static charge on each one.

Current electricity refers to the behavior of electrical charges in motion. In order for charged particles to flow, some pathway must be provided

for them. That pathway is called an electric circuit. An electric circuit typically consists of a source of electricity, such as a battery; an appliance that operates on electric energy, such as a toaster; a meter that measures the flow of electrons, such as a galvanometer; and metal wires connecting those parts of the circuit.

Electric charge

The two kinds of electric chargespositive and negativehave the same magnitude (size, force, or intensity) but opposite effects. The magnitude of an electric charge has been measured very accurately and been found to be 1.602189 × 1019 coulomb. The unit used in measuring electric charge (coulomb; C) was named after French physicist Charles Augustin de Coulomb (17361806), an early authority on electrical theory. The coulomb is a fundamental property of matter, like the mass of an electron, the gravitational constant, and the speed of light.

Since a single positive charge and a single negative charge have the same magnitude, their combination produces a net charge of zero. That is, +1.602189 × 1019 C + 1.602189 × 1019 C = 0. All atoms normally have equal numbers of protons and electrons and are, therefore, electrically neutral. This fact explains the absence of electrical phenomena in everyday life. A person walking across ordinary grass normally does not get a shock because grass, dirt, and air are all made of electrically neutral atoms.

Only when electrons or protons begin to accumulate do electrical events occur. One such effect can be observed when a person shuffles across a carpet. Friction transfers charges between shoe soles and carpet, resulting in the familiar electrical shock when the excess charge sparks to a nearby person. Lightning is another phenomenon caused by the accumulation of electric charges. At some point, those charges become so large that they jump from one cloud to another cloudor between ground and cloudproducing a lightning bolt.

Electric fields

Any charged particle alters the space around it. For comparison, think of any object in space, such as a planet. The region around that object (in this case, the space around the planet) is affected by the object's (the planet's) presence. We call that effect gravity. A second object placed in the gravitational field of the first object is attracted to the first object. A space probe sent in the direction of another planet, for example, is pulled toward that planet's surface by gravitational attraction.

Electric charges have similar effects. Imagine a ping-pong ball carrying a negative charge is suspended in the air by means of a silk thread. Then, a second ping-pong ball is placed in the vicinity of (or near to) the first ball. The second ping-pong ball will be attracted to or repelled by the first ping-pong ball. The second ball experiences a force of attraction or repulsion caused by the nature of the electric charge on the first ball. The region in space over which that force exists is called an electric field.

Coulomb's law

The law describing the force between charged particles was discovered by Coulomb in 1777. Electrical force, Coulomb found, depends on two factors: the electric charge on any two objects and the distance between them. That force can be expressed as an inverse square law. That is, the force between two charged particles decreases as the distance between them increases. When the distance is doubled (increased by 2), the force is reduced by one-fourth (½2). When the distance is tripled, the force is reduced by one-ninth (3). And when the distance is made ten times as great, the forced is reduced by .

Electrical properties

Potential difference. Any collection of electric charges (such as a large mass of electrons) has certain characteristic properties, including potential difference and current flow. Potential difference, also called voltage, is the amount of electric energy stored in a mass of electric charges compared to the energy stored in some other mass of charges.

Imagine a small box into which electrons can be pumped. Pushing the first few electrons into the box is not difficult. But the more electrons in the box, the more difficult it is to add additional electrons. Electrons are all negatively charged, so they repel each other. Adding electron number 1,001 to the box, for example, is difficult because it must overcome the repulsion of 1,000 electrons already in the box. Adding electron number 10,001 is even more difficult.

The more electrons that have been accumulated, therefore, the greater their pressure to escape. The giant spark machines that are sometimes displayed at science fairs illustrate this point. Electrons are added to one of two large metal balls that make up the machine. Normally the air between the two balls is a nonconductor of electricity: it does not permit the flow of electrons from one ball to the other. At some point, however, the number of electrons on the first ball becomes too large to maintain this nonconductive statethe potential difference between it and the second ball is just too great. Many electrons jump all at once from the first ball to the second ball, producing a giant electric spark.

Potential difference is responsible for the operation of all electric appliances. Electric power companies build power plants where huge amounts of electric charge are accumulated; in other words, these plants are capable of providing high voltage electric currents. When a consumer turns on a switch, a pathway for that current is provided. Electric charges

rush out of the power plant, through transmission wires, and into the consumer's home. There they flow through and turn on a microwave, a CD player, a television set, a VCR, or some other electric device.

Electric current. The rate at which electric charges flow through a circuit is called current. The formal definition of current (designated by the symbol i) is the number of electric charges (C) that pass a given point in a circuit (a path of current that includes a power source) per second (t). Mathematically, i = C/t.

The unit of current flow is the ampere (amp, or A), named for French physicist André Marie Ampère (17751836). One ampere is defined as the flow of one coulomb (a measurement of electrical charge) of electrons per second.

Electrical resistance. The flow of electrons in a circuit depends on two factors. One factor is the potential difference or voltage in the circuit. The other factor is resistance, a force similar to mechanical friction that reduces the flow of electrons through a material. Nearly all materials have at least some resistance to the flow of electric current. Those with a smaller resistance are said to be conductors of electricity. Those with a greater resistance are called nonconductors, or insulators. The unit of electrical resistance is the ohm (), named for German physicist Georg Simon Ohm (17891854).

The amount of current that flows through an electric circuit can be expressed mathematically by a law discovered by Ohm in 1827. Ohm's law says that the amount of current in a circuit is equal to the potential difference in the circuit divided by the electrical resistance, or i = V/r.

Electric power

The most useful way of expressing the amount of work available from an electric current is electric power. Electric power is defined as the product of the voltage and current in a circuit, or: P = V · i. Thus, a circuit with a high potential difference (voltage) and a large current is a source of a large electric power.

Most people are familiar with the unit for electric power, the watt (W). The watt was named for English inventor James Watt (17361819). One watt is defined as the product of one volt times one ampere, or 1 W = 1 V × 1 A.

Most electric appliances are rated according to the electric power needed to operate them. Ordinary lightbulbs, for example, are likely to be 25 W, 60 W, or 100 W bulbs. At the end of each month, local electric companies send consumers a bill for the amount of electric power used during that time. The bill is based on the number of kilowatts (thousands of watts) and the price per kilowatt in the consumers' area.

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electricity

electricity Form of energy associated with static or moving charges. Charge has two forms – positive and negative. Like charges repel, and unlike attract; as described by Charles Coulomb in Coulomb's law. Electric charges are acted upon by forces when they move in a magnetic field, this movement generates an opposing magnetic field (Faraday's laws). Electricity and magnetism are different aspects of electromagnetism. The flow of charges constitutes a current, which in a conductor consists of negatively charged electrons. For an electric current to exist in a conductor there must be an electromotive force (emf) or potential difference between the ends of the conductor. If the source of potential difference is a battery, the current flows in one direction as a direct current (DC). If the source is the mains, the current reverses direction twice every cycle, as alternating current (AC). The ampere is the unit of current, the coulomb is the unit of charge, the ohm the unit of resistance and the volt is the unit of electromotive force. Ohm's law and the laws of Kirchhoff are the basic means of calculating circuit values.

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electricity

e·lec·tric·i·ty / ilekˈtrisitē; ˌēlek-/ • n. a form of energy resulting from the existence of charged particles (such as electrons or protons), either statically as an accumulation of charge or dynamically as a current. ∎  the supply of electric current to a house or other building for heating, lighting, or powering appliances: the electricity was back on. ∎ fig. a state or feeling of thrilling excitement: the atmosphere was charged with a dangerous sexual electricity.

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Electricity

Electricity

What is Electricity?
U.S. Electricity Usage
The Electric Bill
Deregulation of Electric Utilities
International Electricity Usage
Trends in the U.S. Electrical Power Industry

Since 1879, when Thomas Alva Edison (1847–1931) flipped the first switch to light Menlo Park, New Jersey, the use of electrical power has become nearly universal in the United States.

What is Electricity?

Electricity is a form of energy resulting from the movement of charged particles, such as electrons (negatively charged subatomic particles) and protons (positively charged subatomic particles). For example, static electricity is caused by friction: when one material rubs against another, it transfers charged particles. The zap you might feel and the spark you might see when you drag your feet along the carpet and then touch a metal doorknob demonstrate static electricity—electrons being transferred between you and the doorknob.

Electric current is the flow of electric charge; it is measured in amperes (amps). Electrical power is the rate at which energy is transferred by electric current. A watt is the standard measure of electrical power, named after the Scottish engineer James Watt (1736–1819). The term wattage refers to the amount of electrical power required to operate a particular appliance or device. A kilowatt (kW) is a unit of electrical power equal to 1,000 watts, and a kilowatt-hour (kWh) is a unit of electrical work equal to that done by 1 kW acting for one hour.

Electrical Capacity

The generating capacity of an electrical power plant, which is measured in watts, indicates its ability to produce electrical power. A 1,000-kW generator running at full capacity for one hour supplies 1,000 kWh of power. That generator operating continuously for an entire year will produce nearly 8.8 million kWh of electricity (1,000 kW C2 24 hours per day C2 365 days per year). However, no generator can operate at 100% capacity during an entire year because of legal restrictions and downtime for routine maintenance and outages. On average, about one-fourth of the generating capacity of an electrical plant is not available at any given time.

Electricity demands vary daily and seasonally, so the continuous operation of electrical generators is usually not necessary. Utilities depend on steam, nuclear energy, and large hydroelectric plants to meet routine demand. Auxiliary gas, turbine, internal combustion, and smaller hydroelectric plants are used during short periods of high demand.

An Electric Power System

An electric power system has several components. Figure 8.1 illustrates a simple electric system. Generating units (power plants) produce electricity, transmission lines carry electricity over long distances, and distribution lines deliver the electricity to customers. Substations connect the pieces of the system together, and energy control centers coordinate the operation of all the components.

U.S. Electricity Usage

In 2007 net generation of electricity totaled nearly 4.2 trillion kWh. Table 8.1 shows that electricity use in the United States—measured by the retail sales of utility companies—has increased nearly every year since 1949. In the thirty years between 1977 and 2007, retail sales of electricity nearly doubled, from 1.9 trillion kWh to 3.7 trillion kWh.

According to the Energy Information Administration (EIA), in Annual Energy Review 2007 (June 2008, http://www.eia.doe.gov/aer/pdf/aer.pdf), coal has been and continues to be the most-used raw source for electricity production in the United States. It accounted for approximately 2 trillion kWh of electricity in 2007, supplying 49% of the net amount of 4.2 trillion kWh of electricity generated. (See Figure 8.2.) Natural gas was the second-largest source of net generation of electricity (893 billion kWh, or 21%), followed by nuclear power (807 billion kWh, or 19% of the total) and hydroelectric power, a renewable energy source (248 billion kWh, or 6%). Very little electricity (103 billion kWh, 2.5%) was generated by all other renewable sources combined, such as geothermal, solar, and wind power.

From 1949 to the early 1990s the industrial sector was the largest consumer of electricity in the United States. (See Table 8.2.) Since then sales to the residential sector have been higher. Beginning in 1998 sales in the commercial sector became higher than sales in the industrial sector. In 2007 about 1.4 trillion kWh went to residential users, 1.3 trillion kWh to commercial customers, and 1 trillion kWh to industrial users.

The consumption of electricity in general is growing because electricity is being used increasingly to perform tasks that were once done with coal, natural gas, or human muscle: manufacturing steel, assembling cars, and milking cows. Electricity is used extensively in technology fields, such as the computer industry, and residential and commercial customers need electricity to run appliances and machinery, such as air conditioners.

The Electric Bill

The cost of electricity is affected by the amount of energy used to create the electricity and move it to the consumer. In 2007, for example, about 42.1 quadrillion British thermal units (Btu) of energy were consumed by U.S. utilities to generate 14.9 quadrillion Btu of electricity. (See Figure 8.3.) After accounting for energy used by the power plants themselves, only 14.2 quadrillion Btu were net generation—the amount available for transmission to customers. Almost 27.2 quadrillion Btu were lost when fuel was converted, and about 1.3 quadrillion Btu were lost during transmission and distribution (labeled “T & D losses” in Figure 8.3). In the end, for every three units of energy that were converted to create electricity in 2007, slightly less than one unit actually reached the end user.

TABLE 8.1 Electricity overview, selected years 1949–2007
SOURCE: Adapted from “Table 8.1. Electricity Overview, Selected Years, 1949–2007 (Billion Kilowatthours),” in Annual Energy Review 2007, U.S. Department
of Energy, Energy Information Administration, Office of Energy Markets and End Use, June 2008, http://www.eia.doe.gov/aer/pdf/aer.pdf (accessed June 28,
2008). Non-U.S. governmental data from the National Energy Board of Canada for the years 1990–2007 and the California Independent System Operator for
the years 2001–07.
[Billion kilowatthours]
Net generation Trade
Importsa Exportsa Net importsa End use
Year Electric power sectorb Commercial sectorc Industrial sectord Total From Canada Total To Canada Total Total T &D lossese and unaccounted forf Retail salesg Direct useh Total
1949291NA5296NA 2NA (s)243255NA 255
1950329NA5334NA 2NA (s)244291NA 291
1955547NA3550NA 5NA (s)458497NA 497
1960756NA4759NA 5NA 1576688NA 688
19651,055NA31,058NA 4NA 4(s)104954NA 954
19701,532NA31,535NA 6NA 421451,392NA 1,392
19711,613NA31,616NA 7NA 441501,470NA 1,470
19721,750NA31,753NA 10NA 381661,595NA 1,595
19741,867NA31,870NA 15NA 3131771,706NA 1,706
19762,038NA32,041NA 11NA 291941,855NA 1,855
19772,124NA32,127NA 20NA 3171971,948NA 1,948
19782,206NA32,209NA 21NA 1202112,018NA 2,018
19802,286NA32,290NA 25NA 4212162,094NA 2,094
19822,241NA32,244NA 33NA 4291872,086NA 2,086
3351982,151NA 2,151
19842,416NA32,419NA 42NA 3401732,286NA 2,286
19862,487NA32,490NA 41NA 5361582,369NA 2,369
19882,704NA32,707NA 39NA 7321612,578NA 2,578
19902,90161313,0381618161622032,7131252,837
19922,93461433,084262823252122,7631342,897
19943,08981513,248454712452112,9351463,081
19963,28491513,444424323402313,1011533,254
19983,45791543,62040401214262213,2641613,425
20003,63881573,80249491315342443,4211713,592
16222023,3941633,557
20023,69871533,85837371516212483,4651663,632
20033,72171553,8832930242462283,4941683,662
20043,80881543,97133342223112663,5471683,716
20053,90281454,0554345192025R2693,661R150R3,811
2006R3,9088R148R4,065R42R43R23R2418R266R3,670R147R3,817
2007P4,00691454,16050512020312993,748E1443,892
aElectricity transmitted across U.S. borders. Net imports equal imports minus exports.
bElectricity-only and combined-heat-and-power (CHP) plants within the NAICS 22 category whose primary business is to sell electricity, or electricity and heat, to the public. Through 1988, data are for electric utilities only; beginning in 1989, data are for electric utilities and independent power producers.
cCommercial combined-heat-and-power (CHP) and commercial electricity-only plants.
dIndustrial combined-heat-and-power (CHP) and industrial electricity-only plants. Through 1988, data are for industrial hydroelectric power only.
eTransmission and distribution losses (electricity losses that occur between the point of generation and delivery to the customer).
fData collection frame differences and nonsampling error.
gElectricity retail sales to ultimate customers by electric utilities and, beginning in 1996, other energy service providers.
8Use of electricity that is 1) self-generated, 2) produced by either the same entity that consumes the power or an affiliate, and 3) used in direct support of a service or industrial process located within the same facility or group of facilities that house the generating equipment. Direct use is exclusive of station use.
R = Revised.
P = Preliminary.
E = Estimate.
NA = Not available.
(s) = Less than 0.5 billion kilowatthours.
Notes: Totals may not equal sum of components due to independent rounding.
Web pages: For all data beginning in 1949, see http://www.eia.doe.gov/emeu/aer/elect.html. For related information, see http://www.eia.doe.gov/fuelelectric.html.

Between 1960 and 1970 the price of electricity declined, but it began to increase during the 1970s because of an oil embargo by the Organization of the Petroleum Exporting Countries. (See Figure 8.4.) From the mid-1980s to 2002 the price of electricity dropped because prices of energy resources declined. After that time, electricity prices began to climb, and prices often varied by location. As Figure 8.5 shows, in 2006 electricity was the most expensive in Hawaii, Massachusetts, New York, Connecticut, Rhode Island, New Hampshire, Alaska, and California, respectively. According to the EIA, in Electric Power Annual 2006 (November 2007, http://www.eia.doe.gov/cneaf/electricity/epa/epa.pdf), the average price of electricity sold to the residential sector was 10.4 cents per kWh in 2006, whereas the commercial sector paid 9.4 cents per kWh. Industrial users paid only 6.1 cents per kWh because the huge amounts of electricity they use allowed them to receive volume discounts. The average price for all sectors across the United States in 2006 was 8.9 cents per kWh.

Deregulation of Electric Utilities

Regulated by the government for decades, electric utilities in some states have passed through a controversial shift toward unregulated markets and increased competition. In 1978 Congress passed the Public Utilities Regulatory Policies Act, which required utilities to buy electricity from private companies when that would be cheaper than building their own power plants. The Energy Policy Act of 1992 gave other electricity generators greater access to the market, resulting in widespread debates about regulatory, economic, energy, and environmental policies. State public utility commissions conducted proceedings and crafted rules related to competition.

California was a leader in deregulation. In the summer of 2000, however, the state experienced rolling electrical blackouts, and electricity bills doubled for many customers. Fearful of similar blackouts and price spikes, most other states had slowed or stopped their efforts to deregulate their electricity markets by the spring of 2001. At that time, twenty-four states and the District of Columbia had begun deregulation. Then, during an investigation of Enron Corporation, documents were found that showed how Enron’s electricity traders had boosted profits with strategies that added to electricity costs and congestion on transmission lines. As a result, public confidence in power companies, in general, and deregulation,

TABLE 8.2 Electricity end use, selected years 1949–2007
SOURCE: Adapted from “Table 8.9. Electricity End Use, Selected Years, 1949–2007 (Billion Kilowatthours),” in Annual Energy Review 2007, U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, June 2008, http://www.eia.doe.gov/aer/pdf/aer.pdf (accessed June 28, 2008)
[Billion kilowatthours]
Retail salesa Discontinued retail sales series
Year Residential Commercialb Industrialc Transportationd Total retail salese Direct usef Total end useg Commercial (old)h Other (old)i
194967E59123E6255NA2554520
195072E66146E7291NA2915122
1955128E103260E6497NA4977929
1960201E159324E3688NA68813132
1965291E231429E3954NA95420034
1970466E352571E31,392NA1,39230748
1971500E377589E31,470NA1,47032951
1972539E413641E31,595NA1,59535956
1974578E440685E31,706NA1,70638558
1976606E492754E31,855NA1,85542570
1978674E531809E32,018NA2,01846173
198071755981532,094NA2,09448874
198273060974532,086NA2,08652686
198478066483842,286NA2,28658385
198681971583142,369NA2,36963189
198889378489652,578NA2,57869990
199092483894652,7131252,83775192
199293685097352,7631342,89776193
19941,0089131,00852,9351463,08182098
19961,0839801,03453,1011533,25488798
19981,1301,0781,05153,2641613,425979104
20001,1921,1591,06453,4211713,5921,055
20021,2651,20599063,4651663,6321,104106
20031,2761,1991,01273,4941683,662
20041,2921,2301,01873,5471683,716
20051,3591,2751,01983,661R150R3 811
2006R1,352R1,300R1,011R7R3,670R147R3,817
2007P1,3921,3431,00683,748E1443,892
aElectricity retail sales to ultimate customers reported by electric utilities and, beginning in 1996, other energy service providers.
bCommercial sector, including public street and highway lighting, interdepartmental sales, and other sales to public authorities.
cIndustrial sector. Through 2002, excludes agriculture and irrigation; beginning in 2003, includes agriculture and irrigation.
dTransportation sector, including sales to railroads and railways.
eThe sum of “residential,” “commercial,” “industrial,” and “transportation.”
fUse of electricity that is 1) self-generated, 2) produced by either the same entity that consumes the power or an affiliate, and 3) used in direct support of a service or industrial process located within the same facility or group of facilities that house the generating equipment. Direct use is exclusive of station use.
gThe sum of “total retail sales” and “direct use.”
h“Commercial (old)” is a discontinued series—data are for the commercial sector, excluding public street and highway lighting, interdepartmental sales, and other sales to public authorities.
i“Other (old)” is a discontinued series—data are for public street and highway lighting, interdepartmental sales, other sales to public authorities, agriculture and irrigation, and transportation including railroads and railways.
R = Revised.
P = Preliminary.
E = Estimate.
NA = Not available.
— = Not applicable.
Note: Totals may not equal sum of components due to independent rounding.
Web pages: For all data beginning in 1949, see http://www.eia.doe.gov/emeu/aer/elect.html. For related information, see http://www.eia.doe.gov/fuelelectric.html.

in particular, eroded. As of February 2003, only seventeen states plus the District of Columbia were actively engaged in restructuring their utilities. (See Figure 8.6.) In addition, five states had delayed deregulation, and California had suspended its restructuring activities. Restructuring was not active in twenty-seven states.

By the last half of the first decade of the 2000s it was becoming widely known that the deregulation of electric utilities, which had occurred in some states as indicated in Figure 8.6, had done little to bring electric prices down. A comparison of Figure 8.5 and Figure 8.6 shows that many of the states in which restructuring and deregulation activity was active in 2003 were states in which electricity prices were the highest in 2006. John Funk reports in “Electric Deregulation: A Legacy of Problems; Consumers Never Got Expected Benefits” (Plain Dealer [Cleveland, Ohio], December 8, 2007) that by late 2007 only eleven states were still deregulated.

International Electricity Usage

World Production

The EIA notes in Annual Energy Review 2007 that in 2005 approximately 17.3 trillion kWh of electricity were generated around the world: 11.5 trillion kWh from fossil fuels, 2.9 trillion kWh from hydroelectric power, 2.6 trillion kWh from nuclear power sources, and 0.4 trillion kWh from wood, waste, wind, and other sources. (See Figure 8.7.) The United States accounted for nearly 4.1 trillion kWh (23%); China, 2.4 trillion kWh (14%); Japan, 1 trillion kWh (6%); and Russia, 904 billion kWh (5%). Figure 8.8 shows net generation of electricity by the type of fuel used and by regions of the world.

World Consumption

In International Energy Annual 2005 (October 2007, http://www.eia.doe.gov/iea/elec.html), the EIA explains that total world electricity consumption increased from 7.3 trillion kWh in 1980 to 15.7 trillion kWh in 2005. Asia and Oceania used 5.1 trillion kWh (32%) in 2005; North America, 4.5 trillion kWh (29%); Europe, 3.2 trillion (21%); and Eurasia, 1.1 trillion (7%). Central and South America used about 4% of the world’s electricity, and the Middle East and Africa each consumed about 3%.

Trends in the U.S. Electrical Power Industry

In Annual Energy Outlook 2008 (June 2008, http://www.eia.doe.gov/oiaf/aeo/pdf/0383(2008).pdf), the EIA predicts that from 2006 to 2030 total electricity consumption will grow at a rate of 1.1% annually. Even though demand will be high for products that use electricity, the efficiency of those products will be high, thereby tempering the demand. Population shifts to warmer climates are expected to increase the use of electricity for cooling.

The demand for electricity in the United States has always been related to economic growth. However, electricity use is expected to grow more slowly than the gross domestic product (a measure of economic growth). Figure 8.9 shows how electricity sales are related more to economic growth than to population growth. Note that the phrase “five-year moving average” means that each point on the graph is an average for that year’s data plus the previous four years’ data. This type of averaging is used to determine long-term averages without the weight of cyclical influences such as the weather.

The rate of growth of consumption carries financial risks for electric companies. If the industry underestimates future needs for electricity, consumers may experience power shortages or losses. By contrast, excessive projections of the nation’s needs may mean billions of dollars spent on unneeded equipment.

The EIA estimates that the United States will need 263 gigawatts (GW) of new generating capacity from 2007 to 2030 to meet growing demand for electricity and to replace aging power plants, most of it after 2015. From 2007 to 2030, 45 GW of capacity are expected to be taken out of production, mainly old fossil-fired plants that are not competitive with newer types of fossil-fired plants.

According to the EIA, the high cost of natural gas, petroleum, and coal as well as increasing prices for new electricity generating capacity led to a jump in electricity prices from 2000 through 2006. Furthermore, electricity prices are forecast to continue increasing through 2009. In 2009 electricity prices are expected to be at an annual average of 9.3 cents per kWh (in 2006 dollars). By 2015, however, as new sources of natural gas and coal are brought on line, electricity prices should fall to 8.5 cents per kWh. After 2015 natural gas and petroleum prices will rise, but electricity producers will rely more on coal and renewables for power generation. The result will be a slow rise in electricity prices to 8.8 cents per kWh in 2030.

Continued concerns about pollution and global warming could result in tightened environmental emission standards, which could, in turn, affect electrical utility expansion, supply, and prices. Advances in solar and wind turbine technology could make renewable sources of electrical power more economical. Some energy experts and environmentalists claim that increased efficiency and conservation efforts are the most sensible alternatives to new construction or to the burning of more fossil fuels in existing plants. Using this idea to its fullest, the former vice president and Nobel Peace Prize winner Al Gore Jr. (1948–) challenges the nation in “A Generational Challenge to Repower America” (July 17, 2008, http://blog.algore.com/2008/07/) to generate all electricity in the United States using only non carbon based renewable resources such as wind, solar, and geothermal power by 2018.

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Electricity

Electricity

Electrical charge

Electric fields

Coulombs law and the forces between electrical charges

Current

Voltage

Resistance

Ohms law

Electrical power

Alternating current and direct current

Resources

Electricity consists of all phenomena resulting from electrical charges at rest and in motion. Our present-day understanding of electrical principles has developed from a long history of experimentation. Electrical technology, essential to modern society for energy transmission and information processing, is the result of our understanding of electricity.

Electrical charge

Electrical charge is a property possessed by a few of the fundamental particles that make up matter. Electrical charge is either positive or negative. Charges with the same sign repel while unlike charges attract. The unit of electrical charge is the coulomb, named for Charles Coulomb, an early authority on electrical theory.

The most obvious sources of electric charge are the negatively-charged electrons from the outer parts of atoms and the positively-charged protons found in atomic nuclei. Electrical neutrality is the most probable condition of matter because most objects contain nearly equal numbers of electrons and protons. Physical activities that upset this balance will leave

an object with a net electrical charge, often with important consequences.

Excess static electric charges can accumulate as a result of mechanical friction, as when someone walks across a carpet. Friction transfers charge between shoe soles and carpet, resulting in the familiar electrical shock when the excess charge sparks to a nearby person.

Many semiconductor devices used in electronics are so sensitive to static electricity that they can be destroyed if touched by a technician carrying a small excess of electric charge. Computer technicians often wear a grounded wrist strap to drain away an electrical charge that might otherwise destroy sensitive circuits they touch.

Electric fields

Charged particles alter their surrounding space to produce an effect called an electric field. An electric field is the concept we use to describe how one electric charge exerts force on another distant electric charge. Whether electric charges are at rest or moving, they are acted upon by a force whenever they are within an electric field. The ratio of this force to the amount of charge is the measure of the fields strength.

An electric field has vector properties in that it has both a unique magnitude and direction at every point in space. An electric field is the collection of all these values. When neighboring electrical charges push or pull each other, each interacts with the electric field produced by the other charge.

Electric fields are imagined as lines of force that begin on positive charges and end on negative charges. Unlike magnetic field lines, which form continuous loops, electric field lines have a beginning and an ending. This makes it possible to block the effects of an electric field. An electrically conducting surface surrounding a volume will stop an external electric field. Passengers in an automobile may be protected from lightning strikes because of this shielding effect. An electric shield enclosure is called a Faraday cage, named for Michael Faraday.

Coulombs law and the forces between electrical charges

Force, quantity of charge, and distance of separation are related by a rule called Coulombs law. This law states that the force between electrical charges is proportional to the product of their charges and inversely proportional to the square of their separation.

The Coulomb force binds atoms together to form chemical compounds. It is this same force that accelerates electrons in a TV picture tube, giving energy to the beam of electrons that creates the television picture. It is the electric force that causes charge to flow through wires.

The electric force also binds electrons to the nuclei of atoms. In some kinds of materials, electrons stick tightly to their respective atoms. These materials are electrical insulators that cannot carry a significant current unless acted upon by an extremely strong electrical field. Insulators are almost always nonmetals. Metals are relatively good conductors of electricity because their outermost electrons are easily removed by an electric field. Some metals are better conductors than others, silver being the best.

Current

The basic unit of electric current is the ampere, named for the French physicist Andre Marie Ampere. One ampere equals 1 coulomb of charge drifting past a reference point each second.

Voltage

Voltage is the ratio of energy stored by a given a quantity of charge. Work must be performed to crowd same-polarity electric charges against their mutual repulsion. This work is stored as electrical potential energy, proportional to voltage. Voltage may also be thought of as electrical pressure.

The unit of voltage is the volt, named for Alessandro Volta. One volt equals one joule for every coulomb of electrical charge accumulated.

Resistance

Ordinary conductors oppose the flow of charge with an effect that resembles friction. This dissipative action is called resistance. Just as mechanical friction wastes energy as heat, current through resistance dissipates energy as heat. The unit of resistance is the ohm, named for Georg Simon Ohm. If 1 volt causes a current of 1 ampere, the circuit has 1 unit of resistance. It is useful to know that resistance is the ratio of voltage to current.

Mechanical friction can be desirable, as in automobile brakes, or undesirable, when friction creates unwanted energy loss. Resistance is always a factor in current electricity unless the circuit action involves an extraordinary low-temperature phenomenon called superconductivity. While superconducting materials exhibit absolutely no resistance, these effects are confined to temperatures so cold that it is not yet practical to use superconductivity in other than exotic applications.

Ohms law

Ohms law defines the relationship between the three variables affecting simple circuit action. According to Ohms law, current is directly proportional to the net voltage in a circuit and current is inversely proportional to resistance.

Electrical power

The product of voltage and current equals electrical power. The unit of electrical power is the watt, named for James Watt. One watt of electrical power equals 1 joule per second. If 1 volt forces a 1-ampere current through a 1-ohm resistance, 1 joule per second will be wasted as heat. That is, 1 watt of power will be dissipated. A 100-watt incandescent lamp requires 100 joules for each second it operates.

Electricity provides a convenient way to connect cities with distant electrical generating stations. Electricity is not the primary source of energy, rather it serves

KEY TERMS

Ampere A standard unit for measuring electric current.

Conductors Materials that permit electrons to move freely.

Coulomb force Another name for the electric force.

Electric field The concept used to describe how one electric charge exerts force on another, distant electric charge.

Generator A device for converting kinetic energy (the energy of movement) into electrical energy.

Insulator An object or material that does not conduct heat or electricity well.

Joule The unit of energy in the mks system of measurements.

Ohm The unit of electrical resistance.

Semiconductor devices Electronic devices made from a material that is neither a good conductor or a good insulator.

Volt A standard unit of electric potential and electromotive force

Watt The basic unit of electrical power equal to 1 joule per second.

as the means to transport energy from the source to a load. Electrical energy usually begins as mechanical energy before its conversion to electrical energy. At the load end of the distribution system the electrical energy is changed to another form of energy, as needed.

Commercial electrical power is transported great distances through wires, which always have significant resistance. Some of the transported energy is unavoidably wasted as heat. These losses are minimized by using very high voltage at a lower current, with the product of voltage and current still equal to the power required. Since the energy loss increases as the square of the current, a reduction of current by a factor of 1/100 reduces the power loss by a factor of 1/10, 000. Voltage as high as 1, 000, 000 volts is used to reduce losses. Higher voltage demands bigger insulators and taller transmission towers, but the added expense pays off in greatly-reduced energy loss.

Alternating current and direct current

Direct current, or DC, results from an electric charge that moves in only one direction. A cars battery, for example, provides a direct current when it forces electrical charge through the starter motor or through the cars headlights. The direction of this current does not change.

Current that changes direction periodically is called alternating current, or AC. Our homes are supplied with alternating current rather than direct current because the use of AC makes it possible to step voltage up or down, using an electromagnetic device called a transformer. Without transformers to change voltage as needed, it would be necessary to distribute electrical power at a safer low voltage but at a much higher current. The higher current would increase the transmission loss in the power lines. Without the ability to use high voltages, it would be necessary to locate generators near locations where electric power is needed.

Southern California receives much of its electrical power from hydroelectric generators in the state of Washington by a connection through an unusually long DC transmission line that operates at approximately one million volts. Electrical power is first generated as alternating current, transformed to a high voltage, then converted to direct current for the long journey south. The direct-current power is changed back into AC for final distribution at a lower voltage. In certain applications, such as this one, the use of direct current more than compensates for the added complexity of the AC to DC and DC to AC conversions.

Resources

BOOKS

Gibilisco, Stan. Electricity Demystified. New York: McGraw-Hill Professional, 2005.

Keljik, Jeff. Electricity 3: Power Generation and Delivery. 8th ed. Clifton Park, NY: Thomson Delmar Learning, 2005.

Donald Beaty

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Electricity

ELECTRICITY

Electrical and electronic devices and machines have become an integral part of contemporary life, ranging from household appliances and computers to huge industrial machines. When home and business owners pay the monthly bill from the electrical power company for the use of all of these items, they are paying for energy very conveniently delivered over electrical wires from the power company.

Although the delivery of electricity to homes and businesses has been possible only during the past century, static electricity was observed by the ancient Greeks over 2,000 years ago. They also noticed natural magnets, called lodestones, found near the town of Magnesia. These were important discoveries because scientists now know that electricity and magnetism are intimately related. Magnetism is used by power companies to produce the electricity used every day.

ELECTRIC CHARGES AND ELECTRIC FORCE

If the humidity is low, it is common to experience a shock when touching a metal doorknob after walking across a carpeted floor. This is static electricity, and it can be studied by rubbing a hard rubber rod on some fur, and then touching the rod to a small metal ball that is suspended on the end of a silk thread. The ball quickly bounces away from the rod and is repelled by it, as shown in Figure 1a. The rod and the ball are electrified or charged with the same type of (net) charge. Further, when a glass rod is rubbed with silk and touched to a second similar ball, the second ball is repelled by the glass rod, shown in Figure 1b. But when the two balls are brought near each other (without touching), they are clearly attracted to each other as shown in Figure 1c.

In the mid-1700s Benjamin Franklin proposed that there are only two kinds of electrical charge, which he called plus and minus. He defined the net charge on the rubber rod to be negative, and the charge on the glass rod to be positive. Further, charges of the same kind are repelled from each other, while opposite charges are attracted to each other. The amount of electrical charge (often represented by the letter q or Q) is measured in coulombs (abbreviated as C) in the Standard International system of units, called S.I. units.

CHARGES IN THE STRUCTURE OF AN ATOM

Electrons particles in matter with a negative charge were discovered around 1900. All matter is made of tiny atoms packed closely together. The structure of the atom was proposed to be like a tiny solar system, with negative electrons revolving in orbits around a very tiny positive nucleus (see Figure 2). The charge ("e") of the electron is a certain fixed amount: only a millionth of a trillionth of 0.16 coulombs (or 0.16 × 10 -18 C). The total negative charge of all of the electrons in an atom is exactly the same (but of opposite sign) as the charge of the positive nucleus; thus an atom taken as a whole is normally uncharged or "neutral."

Since a piece of matter (e.g., a piece of rubber or copper) is made up of a great many neutral atoms, the piece is itself normally neutral or uncharged. When a rubber rod is rubbed with fur, some electrons are pulled from the fur onto the rod, giving it extra negative charge (the fur is then deficient of electrons so it is positively charged).

ELECTRIC CIRCUITS AND CURRENT FLOW

There were few applications of electricity (or of magnetism) before the invention of the battery by Alessandro Volta in 1800. A battery can cause charges to move for long periods of time. The movement or "flow" of electrical charge is called a current. A basic battery cell consists of two different metals (called electrodes) immersed in an acid or salt solution (called an electrolyte). Through chemical interactions, one electrode develops extra electrons and becomes negatively charged, while the other develops a deficiency of electrons and becomes positively charged; these are respectively labeled the negative (-) and positive (+) battery cell terminals.

Work (W) is done by a battery whenever it pushes a positive charge (+q) away from the (+) terminal (through space outside the battery) to the (-) terminal. The "potential" or "emf" or "voltage" (V) of a battery is defined as the work done in this process divided by the charge: V= W/q. In S.I. units the voltage V is in volts V to honor Volta. A battery cell often used in flashlights is the "carbon-zinc dry cell." If unused and fresh, the carbon-zinc cell has a voltage of about 1.5 V. Many flashlights use two carbon-zinc cells placed end-to-end or in "series." Strictly speaking, the two cells together constitute a "battery," and the voltage of this battery is 3.0 V. The common 12 V "lead-acid" battery used in automobiles has six cells connected in series with it; each lead-acid cell has a voltage of 2.0 V.

Suppose a long thin metal wire is connected by a pair of thick wires between the terminals of a battery. This is a basic "electric circuit" as shown in Figure 3a. In all metals, each atom permits roughly one of the outer electrons to move quite freely in the material; these are called the "free electrons." In contrast, all electrons of the atoms of good electrical "insulators," such as glass, rubber, and air, are tightly bound to the atoms and are not free to move through the body of the material. The free electrons are repelled from the negative battery terminal and attracted toward the positive terminal, so that a continuous movement of charge (an electrical current) results around this complete path or "circuit." But there are frictional effects (electrons bumping into atoms as they move along) that resist the movement or flow of electrons through the wires, especially in the thin wire. The frictional effects result in the electrical "resistance" (R) of the wire, and cause the wires to heat up, especially the long thin wire.

An important property of this or any electrical circuit is the rate that charge moves past a place in the circuit (e.g., out from or into a battery terminal). The electrical current (I) is defined to be the charge (Q) that flows, divided by the time (t) required for the flow: I = Q/t. In S.I. units the current (I) is in amperes (A).

In the early 1800s, Georg Ohm studied the effect on current of changing the battery voltage as well as the length, cross-sectional area, and material of the wire in an electrical circuit like Figure 3a. He found that the current flow (I) was proportional to the voltage (V) and inversely proportional to the resistance (R) of the wire to this flow. The resistance (R) is quite constant for a given piece of metal wire; Ohm's law states that we may write that I=V/R. The S.I. units of resistance are ohms (Ω). The resistance to current flow of a wire is larger if the wire is longer, but smaller if the wire is thicker (larger cross-sectional area).

The smallest diameter copper wire generally permitted within the walls for U.S. household wiring is called no. 14 wiring; such wire has a diameter of about 1/16 inch (1.63 mm). A 10 foot length (about 3 meters) of no. 14 copper wire has a resistance of about 0.025 ohms; note that a 100 foot length (about 30 meters) has a resistance of 0.25 ohms.

Figure 3b shows the basic electrical circuit of Figure 3a as it is drawn using conventional electrical symbols. Note the symbol for a battery. The connecting wires with negligible resistance are drawn as lines, while an element with significant resistance is drawn as a zigzag line. An electrical switch is a length of metal that can be moved so that a space of air appears in the circuit; the air space has a large resistance (perhaps billions of ohms) so that virtually no current flows through it when it is "open" (as represented by the dashed line in Figure 3b. When the switch is closed the circuit path is complete and current flows around the "closed circuit." It is conventional to draw the current flow direction as from the (+) battery terminal to the (-) terminal. This is the direction that (+) charges would move if they were moving within the wire, and this was assumed to be the case from about 1800 to 1900. It is now known electrons move in the opposite direction, but the old conventional direction is almost universally used. In any case, the current flows in only one direction in this circuit; this situation is called "direct current" or "d.c."

ELECTRICAL POWER AND ELECTRICAL ENERGY

As electrical current flows through a wire of significant resistance, the wire is heated and the wire gives off heat energy. The wire in an incandescent light bulb is heated so much that it glows and gives off light energy as well as heat energy. This energy is supplied by a battery or other source of emf. Further, "power" is the rate that energy is being supplied, or that work is being done: power = energy/time, or power = (work done)/time. In S.I. units power is measured in watts. Using the definition of voltage and of current one can show that when a current flows from a battery (or any source of emf), the battery is delivering power at the rate of the voltage times the current: P = VI. For example, suppose a 115 V battery is supplying 0.87 amperes of current to a light bulb connected to the battery; then the power being used by the light bulb is equal to (115V) × (0.87A) = 100 watts. This particular bulb is a "100 watt light bulb." Note that because 1,000 watts equals one kilowatt, this bulb is using a tenth of a kilowatt or 0.10 kilowatts (0.10 kW) of power. ^F0^Since power = energy/time, it follows that energy = power × time; that is, energy supplied is equal to the power multiplied by the time-interval. The unit of electrical energy unit used by the electrical utility company is (kilowatts) × (hours), or kWh. Suppose a 100 W bulb is turned on for one day or 24 hours. The energy used by the bulb is (0.10 kW) × (24 h) = 2.4 kWh. A typical electrical energy cost in the United States might be 8 cents per kWh, so the cost for using this bulb for an entire 24 hour day would be (2.4 kWh) × (8 cents/kWh) = 19.2 cents.

Note that electrical energy used (and paid for) depends not only on the power consumption by a device or appliance, but also the length of time that it is used in a month. Therefore people are sometimes surprised to discover that there is a modest electric bill even after they have been gone from home on vacation and "everything" had been turned off. However, a number of devices around the home were probably operating, such as electric clocks, the electric motor on the furnace, the refrigerator, and the freezer. There are also many applicances operating on standby mode, such as televisions, answering machines, and cordless appliance. These are sometimes called "phantom power" devices.

MAGNETS, MAGNETIC FIELD, AND ELECTROMAGNETS

Magnets also repel or attract each other. A magnet always has both a north pole (N) and a south pole (S). Again, "opposites attract and likes repel" so that two magnets with north poles close to each other are repelled from each other, even without touching. The influence in the region near a magnet is often pictured as a "magnetic field"; invisible "magnetic field lines" are imagined, and often drawn in a diagram of a magnet. Figure 4a illustrates a steel bar "permanent magnet" with its magnetic field lines.

In the early 1800s H. C. Oersted discovered that an electric current flowing through a coil of wire produces a magnetic field, as shown in Figure 4b. A long coil of wire, often wound on an iron core to enhance the magnetic field, is called a "solenoid" or "electromagnet" and attracts iron or steel objects, just like a permanent magnet.

ELECTRIC GENERATOR

Shortly after Oersted's discovery, Michael Faraday found that changing the number of magnetic field lines within a coil of wire induces an emf or voltage in the coil so that a current flows if there is a closed circuit. Thus not only can a current produce a magnetic field, but a changing magnetic field can generate a current. Figure 5a shows the basic idea of an electric generator. A coil consisting of a single turn of wire is pictured; this is twirled (rotated) in front of a bar magnet so that the magnetic field lines pass through the coil, first from one side and then the other side. The changing magnetic field within the coil results in an alternating emf or voltage that is measured between the terminals A and B, and a current that reverses directions (i.e., an alternating current or a.c.) flows through the attached "load" resistance.

The alternating voltage V AB measured between terminals A and B is graphed in Figure 5b. If the coil is turned at 60 cycles per second, then the frequency of alternation is 60 cycles per second (called 60 Hz in S.I. units). This is the standard frequency for commercial a.c. power in the United States (in Europe the standard is 50 Hz). By increasing the number of turns (or loops) in the coil, or by increasing the magnetic field strength, it is possible to increase the amount of emf or voltage generated (e.g., the peak voltage V peak illustrated in Figure 5b). A typical power company generator might generate 10,000 V rms. This is much too large to be safe for household use, so the generated voltage must be "transformed" down to about 115 V rms that is present at a regular household outlet. (But first it is actually transformed up to much higher voltage to reduce energy lost in transporting the electrical energy.)

Note that a.c. voltages (also a.c. currents) are usually measured and quoted as "r.m.s." The r.m.s. value is 70.7 percent of the peak value. This is done so that the formula to calculate electrical power in the a.c. case is the same as for the d.c. case stated earlier: power is the voltage times the current (provided both are rms values).

It is important to realize that it requires effort to turn the coil of an electrical generator if current is being supplied by the generator; that is, work must be done to turn the generator coil. Conservation of energy requires that the energy used to turned the coil (i.e., mechanical energy input to the generator) is at least as much as the electrical energy produced by the generator in a given period of time. Electrical generators have relatively high efficiency, so that the electrical power output is perhaps 90 percent of the mechanical energy input, with the remaining 10 percent lost in various heating effects in the generator. Most commercial (utility company) electrical generator coils in the United States are turned by steam engines that burn coal to obtain the energy to generate the electricity.

TRANSFORMERS AND DELIVERY OF ELECTRIC POWER

Alternating voltage (called a.c. voltage) can be quite readily changed to a different value through the use of an electrical transformer. Note that an electrical transformer will not transform a d.c. voltage to another d.c. voltage value; this is a principal reason why commercial electricity in the United States (and most of the world) is almost always a.c. rather than d.c. A transformer consists basically of two coils of wire, with one coil often wound on top of the other. Electrical voltage is supplied to the coil called the "primary" coil, while voltage is output from the "secondary" coil. Then the basic transformer relationship is that the ratio of the secondary voltage to primary voltage is the same as the ratio of secondary-coil-turns to primary-coil-turns.

Suppose 10,000 V rms (e.g., from an electrical power plant generator) is input to a transformer where the number of secondary turns is 75 times more than the number of primary turns. Then the voltage from the secondary will be 75 × 10,000 V rms = 750,000 V rms. This very high voltage level is actually produced by the secondary of the transformers at a modern commercial electrical power plant; the 750,000 V rms is connected to the high voltage transmission lines (thick wire cables) that are used to transport the electrical power over long distances (perhaps hundreds of miles). The high voltage is used to reduce the energy lost to heating of the transmission wire resistance by the electrical current. The power lost to heating of the transmission wire is proportional to the square of the current flowing, so that the losses mount rapidly as the current flowing increases. But the power transmitted is equal to the transmission line voltage times the current flowing. For a given power, the current flowing will be much less (and energy lost in the transmission process is much less) if the transmission line voltage is very large. At the output end of the transmission line, a transformer is used again to step the voltage down to a level appropriate for local distribution (e.g., 2,400 V rms), and a neighborhood transformer is finally used to step the voltage down to 220V rms and 110 V rms for use in homes and businesses.

Dennis Barnaal

See also: Electric Power, Generation of; Electric Power Transmission and Distribution Systems; Electricity, History of; Transformers.

BIBLIOGRAPHY

Aubrecht, G. (1995). Energy, 2nd ed. Englewood Cliffs, NJ: Prentice-Hall.

Faughn, J.; Chang, R.; and Turk, J. (1995). Physical Science, 2nd ed. Fort Worth, TX: Harcourt College Publishers.

Giancoli, D. (1998). Physics, 5th ed. Upper Saddle River, NJ: Prentice-Hall.

Priest, J. (1991). Energy: Principles, Problems, Alternatives, 4th ed. Reading, MA: Addison-Wesley Publishing Co.

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Electricity

ELECTRICITY

During the last decades of the nineteenth century, electricity brought Europeans a wide variety of innovations that ultimately improved the lives of most people. Among other things, electricity made possible the undersea cable, the electro-magnetic telegraph, and the telephone. It gradually transformed industry, transportation, and for many people, home life.

Although some awareness of electricity had existed as far back in time as classical Greece and the Renaissance, in the eighteenth century observations and discoveries, including those of Benjamin Franklin, became more systematic. In 1820 Hans Oersted (1777–1851), a Danish physicist, noted that a strong current moving through a wire could cause a compass to move, and that currents were mutually attractive if they moved in the same direction but had the opposite effect if they moved in different directions. Oersted's English colleague Michael Faraday (1791–1867) investigated the effects of electromagnetism, discoveries that later influenced the development of electric generators and transformers. In 1866 Werner von Siemens (1816–1892), a German, invented the first dynamo, which made possible the production of great amounts of electrical energy. In 1879 the American Thomas Edison (1847–1931) invented the incandescent electric lamp. Soon after, the development of electric alternators and transformers and improvements in cable and insulation made it possible for electric power to be generated and diffused. The first electrical power stations started up in 1881. By the end of the century, electric streetlights made it easier to find one's way around town at night, and electric tramways could be found in a number of cities. Still, in much of Europe electricity remained a luxury identified with grand hotels, department stores, and wealthy neighborhoods.

European economic growth and particularly industry benefited from electricity during the last two decades of the nineteenth century, in part because electric power could be carried quite easily, replacing water power, coal, and gas in many industries, including textiles, steel, and construction. German industries in particular benefited early on from the transformation effected by electricity. Gradually in many European countries, particularly in western Europe, electric sewing machines, refrigerators, fans, and vacuum cleaners were available to those who could afford them.

The first electric lights were not always located in cities: often the pioneers in the field were factories, as was the case with the Finlayson factory in Tampare, Finland, in 1882 and in Resita, Romania, in a metallurgical factory that same year. As a rule, the new lighting system was first tried out in the smaller factories before bids were extended to large cities. One of the first initiatives of the kind occurred in Hungary. Following the successful modernization of corn mills, in 1878 a young engineer, Károly Zipernowsky, was hired by the Ganz company in Budapest to carry out research with a view toward laying the foundations of an electrotechnological industry in central Europe. However, as occurred in many cities, the Budapest municipality initially rejected the idea of switching from gas to electric lights, reluctant to allocate public money to a technological innovation that remained rather mysterious. The Ganz company nevertheless managed to take the market of public lighting, prevailing over Edison's company (all the more so, as Zipernowsky and his colleagues had made the technological choice of alternating current, which guaranteed more efficient transport). Thanks to its system Ganz eventually served Vienna, Innsbruck, Milan, Turin, Cologne, Lucerne, Sofia, Belgrade, and Stockholm as well as Budapest. In 1906, 44 percent of the electric power produced in Hungary was used for lighting, with Budapest accounting for 60 percent of the electric power produced. In Bohemia, Prague had the largest thermo-electric power plant in the country (coal was very cheap). Setting aside these two countries, use of electric power to provide lighting was not as prevalent in central European nations as it was in western Europe. However, one must consider that a plant providing a city with power used essentially for lighting is in fact underused (it runs at only 10 to 20 percent of its full capacity); to make electric power profitable, providers either had to serve only those areas with high purchasing power or find new markets, such as industry or public transports.

Clearly in these early years electric power was more costly than gas, but in 1882 its Russian advocates promoted it by pointing out that it burned regularly, gave off less heat, did not pollute the air, and did not emit a whizzing sound. All these arguments were used in European cities, especially with regard to gas-powered lights (or those burning kerosene or oil, two other fuels used to provide light in urban areas). In public places such as theaters, which were flooded with light, the heat and smell from lights were as a rule considered a nuisance. Thus with the spread of electric power came an enhanced sense of urban glamour, particularly in capital cities. When world exhibitions were held (for example, in Paris in 1889 and 1900), electricity demonstrated that the capital was a modern city. When Romania became an independent country after the Russo-Turkish War of 1877–1878, Bucharest did its best to show that it had achieved the status of European capital. In this case authorities strongly supported the first attempts to provide the city with electric lighting, and in 1882 the city accepted a proposal made by the Austrian subsidiary of an English company. However, the most prestigious installation in Europe undeniably was the illumination of Berlin, in particular that of Unter den Linden, together with that of other major thoroughfares in the city. The management of the BEW electric company (a subsidiary of the powerful industrial firm AEG) noticed the public's preference for electric lights, conducive to a livelier nightlife. And in England, the new technology was used to create a lavish show of electrical effects: for Queen Victoria's Golden Jubilee in 1887, electric candelabra reproducing the colors of the rainbow and electric crowns placed on the tops of buildings lined London's streets.

Major cities provided opportunities for comparing the various lighting systems (gas versus electric power, or contrasting electric systems with one another). For example, electric arc lamps and incandescent lamps were compared. The first device made it possible to illuminate large spaces such as public gardens, parks, and squares, but its main drawback was that it was very unpleasant to the eye and could not be divided into smaller lighting units. Conversely, incandescent lamps made the new light much easier to use. At first, when cities put up arc lamps, as was done in Vienna in 1882, the near by streets that were still lit by gas lamps seemed quite dark by comparison. Arc lights were so powerful that some proposed projects involved lighting a whole city with one single source of light. Many city councils tested gas and electrical systems in nearby streets, as was done in Paris in the 1880s. Some cities chose one system over the other, while other cities allowed the two systems to exist side by side; arc lamps and gas lamps coexisted harmoniously, for example, in Berlin. In St. Petersburg in 1914, 47 percent of street lamps burned gas, 37 percent burned kerosene, and 16 percent worked on electric power. In Russia electric power faced competition from kerosene lamps rather than from gas because the country produced cheap oil in large quantities. Before the Bolshevik Revolution, most electrically powered installations were located in Moscow and St. Petersburg but also in Baku, which is surprising unless one considers the rapid expansion of this oil-producing city at the close of the nineteenth century. Finally, it must be noted that all the European capitals boomed with the "war of systems," opposing the proponents of continuous electric current (Edison, to name one), who argued that it was safe, and proponents of alternating electric current (Westing-house and Ganz), which might have resulted in city dwellers running major risks (comparable to those of lightning). The controversy died out when electric power no longer was produced inside towns but farther and farther a field, in which case alternating current became a necessity, and more particularly three-phase current.

Throughout the nineteenth century, the urban consumer had become more demanding, believing that the city must become more and more pleasant and the streets more and more illuminated. Electricity answered this desire by providing a form of lighting that was both easy to use and hygienic, and by the early twentieth century not only lights but also other electric-powered conveniences were passing from the status of a luxury to that of a basic need.

See alsoCities and Towns; Industrial Revolution, Second; Science and Technology; Transportation and Communications.

bibliography

Beltran, Alain, and Patrice A. Carré. La fée et la servante: La société française face à l'eélectriciteé XIX–Xxème siècle. Paris, 1991.

Canby, Edward Tatnall. History of Electricity. New York, 1963.

Coopersmith, Jonathan. The Electrification of Russia 1880–1926. Ithaca, N.Y., 1992.

Hannah, Leslie. Electricity before Nationalisation: A Study of the Development of the Electricity Supply Industry in Britain to 1948. London, 1979.

Hughes, Thomas P. Networks of Power: Electrification in Western Society 1880–1930. Baltimore, Md., and London, 1988.

Marvin, Carolyn. When Old Technologies Were New: Thinking about Electric Communication in the Nineteenth Century. Oxford, U.K., 1988.

Mori, Giorgio, ed. Storia dell'industria elettrica in Italia. Vol. 1: Le origini (1882–1914). Rome, 1992.

Morus, Iwan Rhys. Frankenstein's Children: Electricity, Exhibition, and Experiment in Early-Nineteenth-Century London. Princeton, N.J., 1998.

——. Michael Faraday and the Electrical Century. Cambridge, U.K., 2004.

Myllyntaus, Timo. Electrifying Finland: The Transfer of a New Technology into a Late Industrialising Economy. Houndmills, U.K., and Helsinki, 1991.

Paquier, Serge. Histoire de l'électricité en Suisse. Vol. 1: La dynamique d'un petit pays européen 1875–1939. Geneva, 1998.

Alain Beltran

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Electricity

chapter 8
ELECTRICITY

Since 1879, when Thomas Edison flipped the first switch to light Menlo Park, New Jersey, the use of electrical power has become nearly universal in the United States.

ELECTRICITY DEFINED

Electricity is a form of energy resulting from the movement of charged particles, such as electrons (negatively charged subatomic particles) and protons (positively charged subatomic particles). Static electricity is caused by friction, when one material rubs against another and transfers charged particles. The zap you might feel and the spark you might see when you drag your feet along the carpet and then touch a metal doorknob is static electricity—electrons being transferred between you and the doorknob.

Electric current is the flow of electric charge; it is measured in amperes (amps). Electrical power is the rate at which energy is transferred by electric current. A watt is the standard measure of electrical power, named after the Scottish engineer James Watt. The term "wattage" refers to the amount of electrical power required to operate a particular appliance or device. A kilowatt is a unit of electrical power equal to one thousand watts, while a kilowatt-hour is a unit of electrical work equal to that done by one kilowatt acting for one hour.

Electrical Capacity

The generating capacity of an electrical plant, measured in watts, indicates its ability to produce electrical power. A one-thousand-kilowatt generator running at full capacity for one hour supplies one thousand kilowatthours of power. That generator operating continuously for an entire year could produce 8.76 million kilowatt-hours of electricity (1,000 kilowatts × 24 hours/day × 365 days a year). However, no generator can operate at 100% capacity during an entire year because of downtime for routine maintenance, outages, and legal restrictions. On average, about one-fourth of the potential generating capacity of an electrical plant is not available at any given time.

Electricity demands vary daily and seasonally, so the continuous operation of electrical generators is not necessary. Utilities depend on steam, nuclear, and large hydroelectric plants to meet routine demand. Auxiliary gas, turbine, internal combustion, and smaller hydroelectric plants are normally used during short periods of high demand.

An Electric Power System

An electric power system has several components. Figure 8.1 illustrates a simple electric system. Generating units (power plants) produce electricity, transmission lines carry electricity over long distances, and distribution lines deliver the electricity to customers. Substations connect the pieces of the system together, while energy control centers coordinate the operation of all the components.

U.S. ELECTRICITY USAGE

In 2003, net generation of electricity totaled 3.8 trillion kilowatt-hours. Table 8.1 shows that electric utility retail sales (electricity use) in the United States has increased almost every year since 1949.

In the United States coal has been and continues to be the largest raw source for electricity production, accounting for slightly more than half of the electricity (about 52%) generated in 2003. (See Figure 8.2 and Figure 8.3.) Nuclear power was the second largest source of electricity (approximately 20%), followed by natural gas (14%), hydroelectric power (a renewable energy source, 7%), and petroleum (3%). Very little electricity (2%) was generated in the United States by all other renewable sources combined, such as geothermal, solar, and wind power.

The Energy Information Administration (EIA) of the U.S. Department of Energy (DOE), in its Annual Energy Review 2003 (2004), noted that coal accounted for the

FIGURE 8.1

generation of approximately 2 trillion kilowatt-hours of electricity in 2003, while natural gas contributed 629 billion kilowatt-hours and petroleum only 118 billion kilowatt-hours in all sectors. Nuclear power accounted for 764 billion kilowatt-hours, and hydroelectric generation totaled 275 billion kilowatt-hours. All other renewable energy sources, including geothermal, wood, municipal waste, wind, and solar energy, produced only 84 billion kilowatt-hours in 2003.

From 1949 through the early 1990s the industrial sector was the largest consumer of electricity in the United States, but since then sales to the residential sector have generally been higher because of changing economic factors. In 2001 sales in the commercial sector became higher than in the industrial sector as well. (See Table 8.2.) In 2003 about 1.3 trillion kilowatt-hours went to residential use, 1.0 trillion kilowatt-hours to industrial customers, and 1.1 trillion kilowatt-hours to commercial users.

Consumption of electricity in general is growing because electricity has increasingly taken over the tasks formerly done with coal, natural gas, or human muscle: manufacturing steel, assembling cars, and milking cows. Electricity is being used extensively in technology fields, such as the computer industry. Residential and commercial use of electricity is increasing with new appliances, air conditioners, computers, and many other developing applications.

THE ELECTRIC BILL

The price paid by a consumer for electricity includes the cost of converting energy into electricity from its original form, such as coal, as well as the cost of delivering it. In 2000, according to the EIA's Annual Energy Review 2003 (2004), consumers paid an average of $20.04 per million Btu for the electric power delivered to their residences, compared to only $5.68 per million Btu for natural gas and $12.01 per million Btu for motor gasoline.

TABLE 8.1

Electricity overview, selected years, 1949–2003
(Billion kilowatthours)
Net generation Imports1 Exports1 End use
Year Electric power sector2 Commercial sector3 Industrial sector4 Total From Canada Total To Canada Total T & D losses5 and unaccounted for6 Retail sales7 Direct use8 Total
1Electricity transmitted across U.S. borders with Canada and Mexico.
2Electricity-only and combined-heat-and-power (CHP) plants within the NAICS (North American Industry Classification System) 22 category whose primary business is to sell electricity, or electricity and heat, to the public. Through 1988, data are for electric utilities only; beginning in 1989, data are for electric utilities and independent power producers.
3Commercial combined-heat-and-power (CHP) and commercial electricity-only plants.
4Industrial combined-heat-and-power (CHP) and industrial electricity-only plants. Through 1988, data are for industrial hydroelectric power only.
5Transmission and distribution losses (electricity losses that occur between the point of generation and delivery to the customer).
6Data collection frame differences and nonsampling error.
7Electricity retail sales to ultimate customers by electric utilities and other energy service providers.
8Commercial and industrial facility use of onsite net electricity generation; and electricity sales among adjacent or co-located facilities for which revenue information is not available.
R=Revised.
P=Preliminary.
E=Estimate.
NA=Not available.
(s)=Less than 0.5 billion kilowatthours.
Notes: Totals may not equal sum of components due to independent rounding.
Web Pages: For data not shown for 1951–1969, see http://www.eia.doe.gov/emeu/aer/elect.html.
For related information, see http://www.eia.doe.gov/emei/aer/elect.html.
source: "Table 8.1. Electricity Overview, Selected Years, 1949–2003 (Billion Kilowatthours)," in Annual Energy Review 2003, U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, September 7, 2004, http://www.eia.doe.gov/emeu/aer/pdf/aer.pdf (accessed September 28, 2004)
1949291NA5296NA2NA(s)43255NA255
1950329NA5334NA2NA(s)44291NA291
1955547NA3550NA5NA(s)58497NA497
1960756NA4759NA5NA176688NA688
19651,055NA31,058NA4NA4104954NA954
19701,532NA31,535NA6NA41451,392NA1,392
19711,613NA31,616NA7NA41501,470NA1,470
19721,750NA31,753NA10NA31661,595NA1,595
19731,861NA31,864NA17NA31651,713NA1,713
19741,867NA31,870NA15NA31771,706NA1,706
19751,918NA31,921NA11NA51801,747NA1,747
19762,038NA32,041NA11NA21941,855NA1,855
19772,124NA32,127NA20NA31971,948NA1,948
19782,206NA32,209NA21NA12112,018NA2,018
19792,247NA32,251NA23NA22002,071NA2,071
19802,286NA32,290NA25NA42162,094NA2,094
19812,295NA32,298NA36NA31842,147NA2,147
19822,241NA32,244NA33NA41872,086NA2,086
19832,310NA32,313NA39NA31982,151NA2,151
19842,416NA32,419NA42NA31732,286NA2,286
19852,470NA32,473NA46NA51902,324NA2,324
19862,487NA32,490NA41NA51582,369NA2,369
19872,572NA32,575NA52NA61642,457NA2,457
19882,704NA32,707NA39NA71612,578NA2,578
198922,848441152,967NA26NA152232,6471082,755
19902,90161313,038161816162142,7131142,827
19912,93661333,0742022222132,7621182,880
19922,93461433,0842628232242,7631222,886
19933,04471463,1972931342362,8611282,989
19943,08981513,2484547122242,9351343,069
19953,19481513,3534143242353,0131443,157
19963,28491513,4444243232373,1011463,247
19973,32991543,4924343792323,1461483,294
19983,45791543,620404012142213,2641613,425
19993,53091563,695434313142293,3121833,495
20003,63881573,802494913152313,4211833,605
20013,58071493,73738391616R2153,370RE174R3,544
2002R3,698R7R153R3,858363613R14R241R3,463RE178R3,641
2003P3,691P8P150P3,848P29P30P24P24P179P3,500E175P3,675

FIGURE 8.2

The unit cost of electricity is high because of the amount of energy expended in creating the electricity and moving it to the point of use. In 2003, for example, about 39.6 quadrillion Btu of energy were consumed by electric utilities to generate electricity in the United States, but 13.1 quadrillion Btu was the net generation, after accounting for energy used by the power plants themselves. (See Figure 8.2.) Most of the remaining 25.8 quadrillion Btu was lost during the energy conversion process. Additionally, about 1.2 quadrillion Btu is lost during the transmission and distribution process (T & D losses). In the end, for every three units of energy that are converted to create electricity, slightly less than one unit actually reaches the end user.

Between 1960 and 1970, the price of electricity declined, but it began to increase during the 1970s because of the OPEC (Organization of the Petroleum Exporting Countries) oil embargo. (See Figure 8.4.) From the mid-1980s to 2003 the price of electricity, in general, dropped because of the decline in energy resource prices. Prices varied depending upon the location. As Figure 8.5 shows, in 2002 electricity was most expensive in the New England states, New York, New Jersey, Pennsylvania, California, Nevada, Alaska, and Hawaii. According to the EIA's Electric Power Annual 2002 (December 2003), the average price of electricity sold to the residential sector was 8.5 cents per kilowatt-hour in 2002, while the commercial sector paid 7.9 cents per kilowatt-hour. Industrial users paid less per kilowatt-hour, 4.9 cents in 2002, because the huge amounts of electricity they use allow them to receive volume discounts. The average price for all sectors across the United States in 2002 was 7.2 cents.

DEREGULATION OF ELECTRIC UTILITIES

Regulated for decades as "natural monopolies," much like the railroad and telecommunications industries, electric

FIGURE 8.3

utilities are in the midst of a radical, highly controversial shift toward unregulated markets and increased competition. In 1978 Congress passed the Public Utilities Regulatory Policy Act (PURPA; PL 95-617), which required that utilities buy electricity from private companies when that would be a lower-cost alternative to building their own power plants. The Energy Policy Act of 1992 (PL 102-486) gave other generators greater access to the market, resulting in a flurry of activity in state and federal legislatures as a host of interest groups debated regulatory, economic, energy, and environmental policies. State public utility commissions conducted proceedings and designed rules related to competition in the electric utility industry.

California was a leader in deregulation activities. In the summer of 2000, however, the state experienced rolling blackouts and electricity bills doubled for many. Fearful of the blackouts and price spikes that afflicted California, by the spring of 2001 most other states had slowed or stopped their efforts to deregulate their electricity markets. At that time, twenty-four states and the District of Columbia had begun deregulation. Then, during an investigation of Enron Corporation, documents were found that showed that Enron electricity traders used strategies that added to electricity costs and congestion on transmission lines for their own profit. These revelations lowered public confidence in power companies in general. As a result of these events and an eroding confidence in deregulation, only seventeen states plus the District of Columbia were actively engaged in restructuring activities as of February 2003, as shown in Figure 8.6 from the

FIGURE 8.4

Energy Information Administration (EIA). In addition, five states had delayed the restructuring process, and one state (California) suspended its restructuring activities. Restructuring was not active in twenty-seven states.

TABLE 8.2

Electricity end use, selected years, 1949–2003
(Billion kilowatthours)
Retail sales1
Year Residential Commercial2 Industrial2 Other3 Total Direct use4 Total
1Electricity retail sales to ultimate customers by electric utilities and, beginning in 1996, other energy service providers.
2Retail customers are classified as "Commercial" or "Industrial" based on NAICS (North American Industry Classification System) codes or usage falling within specified limits by rate schedule.
3Public street and highway lighting, other sales to public authorities, sales to railroads and railways, and interdepartmental sales.
4Commercial and industrial facility use of onsite net electricity generation; and electricity sales among adjacent or co-located facilities for which revenue information is not available.
R=Revised.
P=Preliminary.
E=Estimate.
NA=Not available.
Note: Totals may not equal sum of components due to independent rounding.
Web Pages: For data not shown for 1951–1969, see http://www.eia.doe.gov/emeu/aer/elect.html. For related information, see http://www.eia.doe.gov/fuelelectric.html.
source: "Table 8.9. Electricity End Use, Selected Years, 1949–2003 (Billion Kilowatthours)," in Annual Energy Review 2003, U.S. Department of Energy, Energy Information Administration, Office of Energy Markets and End Use, September 7, 2004, http://www.eia.doe.gov/emeu/aer/pdf/aer.pdf (accessed September 28, 2004)
1949674512320255NA255
1950725114622291NA291
19551287926029497NA497
196020113132432688NA688
196529120042934954NA954
1970466307571481,392NA1,392
1971500329589511,470NA1,470
1972539359641561,595NA1,595
1973579388686591,713NA1,713
1974578385685581,706NA1,706
1975588403688681,747NA1,747
1976606425754701,855NA1,855
1977645447786711,948NA1,948
1978674461809732,018NA2,018
1979683473842732,071NA2,071
1980717488815742,094NA2,094
1981722514826852,147NA2,147
1982730526745862,086NA2,086
1983751544776802,151NA2,151
1984780583838852,286NA2,286
1985794606837872,324NA2,324
1986819631831892,369NA2,369
1987850660858882,457NA2,457
1988893699896902,578NA2,578
1989906726926902,6471082,755
1990924751946922,7131142,827
1991955766947942,7621182,880
1992936761973932,7631222,886
1993995795977952,8611282,989
19941,0088201,008982,9351343,069
19951,0438631,013953,0131443,157
19961,0838871,034983,1011463,247
19971,0769291,0381033,1461483,294
19981,1309791,0511043,2641613,425
19991,1451,0021,0581073,3121833,495
20001,1921,0551,0641093,4211833,605
20011,2031,0899641143,370RE174R3,544
2002R1,267R1,116R972R107R3,463RE178R3,641
2003P1,280P1,119P991P109P3,500E175P3,675

INTERNATIONAL ELECTRICITY USAGE

World Production

In 2002 approximately 15.3 trillion kilowatt-hours of electricity were generated around the world. (See Figure 8.7.) As reported in the EIA's Annual Energy Review 2003 (2004), the United States accounted for 25% of this production; China, 10.4%; Japan, 6.5%; and Russia, 5.8%. Figure 8.8 shows net generation of electricity by type and by region of the world.

World Consumption

According to the EIA in Annual Energy Review 2003 (2004), world total electricity consumption continued to increase, rising from 353.3 quadrillion Btu in 1993 to 411.6 quadrillion Btu in 2002. North America, Central America, and South America accounted for 34% of the world's total consumption in 2002; Asia and Oceania, 28%; Western Europe, 18%; and Eastern Europe and the former USSR, 13%. The Middle East and Africa used 5% and 3%, respectively. (See Figure 8.9.)

FIGURE 8.5

FUTURE TRENDS IN THE U.S. ELECTRIC INDUSTRY

In Annual Energy Outlook 2004 the EIA predicted that from 2002 to 2025, residential U.S. electricity consumption will grow at a rate of 1.4% annually. This compares with 7% growth per year during the 1960s. Several factors led to this decreased growth of electricity consumption, including increased market saturation of electric appliances and improvements in efficiency. Commercial demand is expected to grow by 2.2% per year because of growth in commercial floor space, while industrial demand will likely increase by 1.6% per year as industrial output rises.

Historically, the demand for electricity in the United States has been related to economic growth. This relationship will continue, but electricity use is expected to grow more slowly than the gross domestic product (GDP), a measure of economic growth. Figure 8.10 shows how electricity sales are related more to economic growth (the GDP) than to population growth. Also, the phrase "five-year moving average" means that each point on the graph is an average of that year and the previous four years'data. This type of averaging is often done to get a better idea of what the real long-term averages would be, without heavy influences on data from cyclical influences, like business or weather cycles.

The issue of electric growth is important and carries financial risks for electric companies. If the industry underestimates future needs for electricity, it could mean power shortages or losses. However, excessive projections of the nation's needs could mean billions of dollars spent on unneeded equipment.

The EIA estimated that the United States will need 356 gigawatts of new generating capacity from 2002 to

FIGURE 8.6

2025 to meet growing demand for electricity and to replace retiring units, most of it after 2010. From 2002 to 2025, sixty-two gigawatts of capacity will most likely be retired, accounting for nearly all old fossil-fired plants that are not competitive with newer types of fossil-fired plants.

The EIA's Annual Energy Outlook 2004 projected that electricity prices will decrease by 8% from 2002 to 2008 and will then remain somewhat stable until 2011. From 2011, however, electricity prices are expected to increase gradually by 0.3% per year to 2025.

Continued concerns about acid rain and global warming could result in tightened environmental emission standards, which may have an impact on electrical utility expansion decisions, prices, and supply. Continued advances in solar and wind turbine technology could make renewable sources of electrical power more economical in the future. Some energy experts and environmentalists claim that increased efficiency and conservation efforts are the most sensible alternatives to new construction or to the burning of more fossil fuels in existing plants.

FIGURE 8.7

FIGURE 8.8

FIGURE 8.9

FIGURE 8.10

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