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.

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).

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 charges—positive and negative—have 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 × 10⁻¹⁹ coulomb. The unit used in measuring electric charge (coulomb; C) was named after French physicist Charles Augustin de Coulomb (1736–1806), 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 × 10⁻¹⁹ C + −1.602189 × 10⁻¹⁹ 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 cloud—or between ground and cloud—producing 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 (⅓³). 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 state—the 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 (1775–1836). 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 (Ω), named for German physicist Georg Simon Ohm (1789–1854).

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 (1736–1819). 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.

electricity was first generated on a commercial basis in Ireland in 1880, by the Dublin Electric Light Company. Initially it was used only as a source of lighting; the company supplied street lighting in the centre of Dublin and won contracts from some leading firms such as Jacobs's biscuit factory. In 1883 the Portrush–Giant's Causeway–Bushmills tram service, on the north Antrim coast, established the first electric railway in Ireland. By the 1890s the majority of electricity generating plants were controlled by local authorities, who were also responsible for distributing current, a situation similar to that in Great Britain. In the Irish Free State the Electricity Supply Board gradually acquired a monopoly over generation and distribution. In Northern Ireland, however, although the Electricity Board of Northern Ireland (established 1931) acquired ownership of the smaller companies, Derry and Belfast corporations and the Larne Electric Light and Power Company continued to supply the greater part of the province's current. In 1942, in response to wartime emergencies, the Ministry of Commerce assumed control of all generating plants.

Mary Daly

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.

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.