- The physical phenomena arising from the behavior of electrons and protons that is caused by the attraction of particles with opposite charges and the repulsion of particles with the same charge.
- The physical science of such phenomena.
- Electric current used or regarded as a source of power.
- Intense, contagious emotional excitement.
electricity
Dictionary:
e·lec·tric·i·ty (ĭ-lĕk-trĭs'ĭ-tē, ē'lĕk-)  |
n.
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| Sci-Tech Encyclopedia: Electricity |
Physical phenomena involving electric charges, their motions, and their effects. The motion of a charge is affected by its interaction with the electric field and, for a moving charge, the magnetic field. The electric field acting on a charge arises from the presence of other charges and from a time-varying magnetic field. The magnetic field acting on a moving charge arises from the motion of other charges and from a time-varying electric field. Thus electricity and magnetism are ultimately inextricably linked. In many cases, however, one aspect may dominate, and the separation is meaningful. See also Electric charge;
The quantitative development of electricity began late in the eighteenth century. J. B. Priestley in 1767 and C. A. Coulomb in 1785 discovered independently the inverse-square law for stationary charges. This law serves as a foundation for electrostatics. See also Coulomb's law; Electrostatics.
In 1800 A. Volta constructed and experimented with the voltaic pile, the predecessor of modern batteries. It provided the first continuous source of electricity. In 1820 H. C. Oersted demonstrated magnetic effects arising from electric currents. The production of induced electric currents by changing magnetic fields was demonstrated by M. Faraday in 1831. In 1851 he also proposed giving physical reality to the concept of lines of force. This was the first step in the direction of shifting the emphasis away from the charges and onto the associated fields. See also Electromagnetic induction; Electromagnetism; Lines of force.
In 1865 J. C. Maxwell presented his mathematical theory of the electromagnetic field. This theory, which proposed a continuous electric fluid, not only synthesized a unified theory of electricity and magnetism, but also showed optics to be a branch of electromagnetism. See also Electromagnetic radiation;
The developments of theories about electricity subsequent to Maxwell have all been concerned with the microscopic realm. Faraday's experiments on electrolysis in 1833 had indicated a natural unit of electric charge, thus pointing toward a discrete rather than continuous charge. The existence of electrons, negatively charged particles, was postulated by A. Lorenz in 1895 and demonstrated by J. J. Thomson in 1897. The existence of positively charged particles (protons) was shown shortly afterward (1898) by W. Wien. Since that time, many particles have been found having charges numerically equal to that of the electron. The question of the fundamental nature of these particles remains unsolved, but the concept of a single elementary charge unit is apparently still valid. See also Baryon; Electrolysis; Electron;
The sources of electricity in modern technology depend strongly on the application for which they are intended.
The principal use of static electricity today is in the production of high electric fields. Such fields are used in industry for testing the ability of components such as insulators and condensers to withstand high voltages, and as accelerating fields for charged-particle accelerators. The principal source of such fields today is the Van de Graaff generator. See also Particle accelerator.
The major use of electricity arises in devices using direct current and low-frequency alternating current. The use of alternating current, introduced by S. Z. de Ferranti in 1885–1890, allows power transmission over long distances at very high voltages with a resulting low-percentage power loss followed by highly efficient conversion to lower voltages for the consumer through the use of transformers. See also Alternating current; Electric current.
Large amounts of direct current are used in the electrodeposition of metals, both in plating and in metal production, for example, in the reduction of aluminum ore. See also Direct current; Electrochemistry; Electrometallurgy; Electroplating of metals.
The principal sources of low-frequency electricity are generators based on the motion of a conducting medium through a magnetic field. The moving charges interact with the magnetic field to give a charge motion that is normal to both the direction of motion and the magnetic field. In the most common form, conducting wire coils rotate in an applied magnetic field. The rotational power is derived from a water-driven turbine in the case of hydroelectric generation, or from a gas-driven turbine or reciprocating engine in other cases. See also Alternating-current generator; Direct-current generator; Electric power generation; Generator.
Many high-frequency devices, such as communications equipment, television, and radar, involve the consumption of only moderate amounts of power, generally derived from low-frequency sources. If the power requirements are moderate and portability is needed, the use of ordinary chemical batteries is possible. Ion-permeable membrane batteries are a later development in this line. Fuel cells, particularly hydrogen-oxygen systems, are being developed. They have already found extensive application in earth satellite and other space systems. The successful use of thermoelectric generators based on the Seebeck effect in semiconductors has been reported. See also Battery; Fuel cell; Ion-selective membranes and electrodes.
The solar battery, also a semiconductor device, has been used to provide charging current for storage batteries in telephone service and in communications equipment in artificial satellites. See also Solar cell.
Direct conversion of mechanical energy into electrical energy is possible by utilizing the phenomena of piezoelectricity and magnetostriction. These have some application in acoustics and stress measurements. Pyroelectricity is a thermodynamic corollary of piezoelectricity. See also Magnetostriction; Piezoelectricity; Pyroelectricity.
| Computer Desktop Encyclopedia: electricity |
The flow of electrons in a circuit. The speed of electricity is the speed of light (approximately 186,000 miles per second or 300,000,000 meters per second). In a wire, it is slowed due to the resistance in the material.
Its pressure, or force, is measured in "volts," and its flow, or current, is measured in "amperes" or simply "amps." The amount of work it produces is measured in "watts" (amps X volts).
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| Britannica Concise Encyclopedia: electricity |
For more information on electricity, visit Britannica.com.
| Columbia Encyclopedia: 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 B.C. 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).
| Law Encyclopedia: Electricity |
This entry contains information applicable to United States law only.
Electricity was discovered by Benjamin Franklin in 1752. The electric generator was invented by Michael Faraday in 1831. Thomas Edison's invention of the electric lightbulb in 1879 sparked the demand for electric power that continues to this day, and initiated 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 (16 U.S.C.A. §§ 791a-828c) was passed in response to increased competition between electric utilities and to 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 1995, a total of thirty-five hundred electric utilities around the United States had the ability to produce over 640 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 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 these IPPs from paying burdensome rates for purchasing backup power from these utilities, and sets the rate at which the utilities can purchase power from these 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.
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 high-voltage power lines.
| Science Dictionary: electricity |
| Electronics Dictionary: electricity |
Science states that certain particles possess a force field or charge. The charge possessed by an electron is negative while the charge possessed by a proton is positive. Electricity can be divided into two groups, static and dynamic. Static electricty deals with charges at rest and dynamic electricity deals with charges in motion.
| Essay: The advent of electricity |
The Greeks and other ancient peoples knew that some substances attract others when one of them has been rubbed. Similarly, they must have encountered mild shocks. People still notice both today, as when clothing picks up lint without touching it or when a doorknob gives a slight shock on a dry winter's day. Thales, often counted as the first scientist, investigated the attractive properties of rubbed amber in Ionia around 600 bce. He compared it to magnetism and noted that it was similar, but different. More than 2000 years later, around 1570, the English scientist William Gilbert also studied magnetism and the corresponding attraction of rubbed amber and various rubbed jewels. He modified the Greek and Latin terms for amber to produce the English word electric as a noun describing a material that behaved like amber. Nearly a hundred years later, in 1650, the term electricity was coined to refer to the force itself.
In the same year that electricity entered English, a German scientist, Otto von Guericke, was working with a method he had developed for making more electricity than could be made by rubbing a small piece of amber. He worked with a different electric, sulfur. He formed this electric into a ball, so it could be rubbed continuously by rotating it. Von Guericke was the first to observe light produced by electricity. Similar experiments produced light from electricity in England.
The electricity produced by von Guericke faded away soon after the ball stopped rotating. Shocks and lights were evanescent experiences. About a hundred years after the use of rotating balls, however, scientists in Leyden (Leiden, the Netherlands) learned that electricity could be stored in water in glass jars and conducted in and out with metal wires or nails. Modern versions are somewhat different in construction, but the main impact of the Leiden jar was the same. A large charge could be stored up over time and then released by touching the conductor. Some terrific shocks resulted, and the jars became popular in parlors as well as with scientists.
Still, no one knew what electricity was. It was not even clear whether there was one type or two (different electrics attracted or repelled different light substances, although the shocks seemed to be the same). Accidentally, a scientist in Italy, Luigi Galvani, found that severed frogs' legs twitched in response to electricity and that they also responded the same way when touching metal that was not charged. Another Italian, Alessandro Volta, who had been experimenting with electricity, found that the reaction was chemical. He built an apparatus, which came to be known as the voltaic pile, that offered the first method of producing electricity in any quantity without rubbing. Improvements on the voltaic pile are the familiar batteries of today.
The main difference between electricity stored in a Leiden jar and that released by a battery is that chemically produced electricity does not all rush out at once. Instead, a steady flow like the current of a river appears. For the first time, electricity became available for periods of time, instead of instants.
Within 20 years, the next key event occurred, also by accident. Hans Christian Oersted discovered that the connection between electricity and magnetism, suspected since at least the time of Thales, was real. An electric current could produce magnetic effects. In another ten years the converse was shown, and magnets were being used to generate electric currents. With the development of powerful currents produced by magnetic generators, the stage was set for the use of electric power for light, for communication, and for production of motion.
| Devil's Dictionary: electricity |
A cynical view of the world by Ambrose Bierce
n.
The power that causes all natural phenomena not known to be caused by something else. It is the same thing as lightning, and its famous attempt to strike Dr. Franklin is one of the most picturesque incidents in that great and good man's career. The memory of Dr. Franklin is justly held in great reverence, particularly in France, where a waxen effigy of him was recently on exhibition, bearing the following touching account of his life and services to science:
"Monsieur Franqulin, inventor of electricity. This
illustrious savant, after having made several voyages around the
world, died on the Sandwich Islands and was devoured by savages,
of whom not a single fragment was ever recovered."
Electricity seems destined to play a most important part in the arts and industries. The question of its economical application to some purposes is still unsettled, but experiment has already proved that it will propel a street car better than a gas jet and give more light than a horse.
| Word Tutor: electricity |
IN BRIEF: A form of energy that comes from the movement of atom particles.
Benjamin Franklin has been credited with the discovery of electricity.
| Wikipedia: Electricity |
"Electric" redirects here. For other uses, see Electric (disambiguation).
Electricity (from the New Latin ēlectricus, "amber-like"[a]) is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction.
In general usage, the word "electricity" is adequate to refer to a number of physical effects. In scientific usage, however, the term is vague, and these related, but distinct, concepts are better identified by more precise terms:
- Electric charge – a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields.
- Electric current – a movement or flow of electrically charged particles, typically measured in amperes.
- Electric field – an influence produced by an electric charge on other charges in its vicinity.
- Electric potential – the capacity of an electric field to do work on an electric charge, typically measured in volts.
- Electromagnetism – a fundamental interaction between the magnetic field and the presence and motion of an electric charge.
Electrical phenomena have been studied since antiquity, though advances in the science were not made until the seventeenth and eighteenth centuries. Practical applications for electricity however remained few, and it would not be until the late nineteenth century that engineers were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricity's extraordinary versatility as a source of energy means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. The backbone of modern industrial society is, and for the foreseeable future can be expected to remain, the use of electrical power.[1]
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Look up electricity in Wiktionary, the free dictionary. |
Contents |
History
Main articles: History of electromagnetism and History of electrical engineering
See also: Etymology of electricity
Long before any knowledge of electricity existed people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BC referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish. They were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians.[2] Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and torpedo rays, and knew that such shocks could travel along conducting objects.[3] Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them.[4] Possibly the earliest and nearest approach to the discovery of the identity of lightning, and electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning (raad) applied to the electric ray.[5]
That certain objects such as rods of amber could be rubbed with cat's fur and attract light objects like feathers was known to ancient cultures around the Mediterranean. Thales of Miletos made a series of observations on static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.[6][7] Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature.[8]
Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English physician William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.[6] He coined the New Latin word electricus ("of amber" or "like amber", from ήλεκτρον [elektron], the Greek word for "amber") to refer to the property of attracting small objects after being rubbed.[9] This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646.[10]
Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky.[11] A succession of sparks jumping from the key to the back of the hand showed that lightning was indeed electrical in nature.[12]
In 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles.[13] Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used.[13] The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819-1820; Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827.[13]
While it had been the early 19th century that had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Nikola Tesla, Thomas Edison, Ottó Bláthy, Sir Charles Parsons, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution.[14]
Concepts
Electric charge
Main article: Electric charge
Electric charge is a property of certain subatomic particles, which gives rise to and interacts with, the electromagnetic force, one of the four fundamental forces of nature. Charge originates in the atom, in which its most familiar carriers are the electron and proton. It is a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system.[15] Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire.[16] The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body, usually caused when dissimilar materials are rubbed together, transferring charge from one to the other.
The presence of charge gives rise to the electromagnetic force: charges exert a force on each other, an effect that was known, though not understood, in antiquity.[17] A lightweight ball suspended from a string can be charged by touching it with a glass rod that has itself been charged by rubbing with a cloth. If a similar ball is charged by the same glass rod, it is found to repel the first: the charge acts to force the two balls apart. Two balls that are charged with a rubbed amber rod also repel each other. However, if one ball is charged by the glass rod, and the other by an amber rod, the two balls are found to attract each other. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. This discovery led to the well-known axiom: like-charged objects repel and opposite-charged objects attract.[17]
The force acts on the charged particles themselves, hence charge has a tendency to spread itself as evenly as possible over a conducting surface. The magnitude of the electromagnetic force, whether attractive or repulsive, is given by Coulomb's law, which relates the force to the product of the charges and has an inverse-square relation to the distance between them.[18][19] The electromagnetic force is very strong, second only in strength to the strong interaction,[20] but unlike that force it operates over all distances.[21] In comparison with the much weaker gravitational force, the electromagnetic force pushing two electrons apart is 1042 times that of the gravitational attraction pulling them together.[22]
The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. By convention, the charge carried by electrons is deemed negative, and that by protons positive, a custom that originated with the work of Benjamin Franklin.[23] The amount of charge is usually given the symbol Q and expressed in coulombs;[24] each electron carries the same charge of approximately −1.6022×10−19 coulomb. The proton has a charge that is equal and opposite, and thus +1.6022×10−19 coulomb. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle.[25]
Charge can be measured by a number of means, an early instrument being the gold-leaf electroscope, which although still in use for classroom demonstrations, has been superseded by the electronic electrometer.[16]
Electric current
Main article: Electric current
The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current.
By historical convention, a positive current is defined as having the same direction of flow as any positive charge it contains, or to flow from the most positive part of a circuit to the most negative part. Current defined in this manner is called conventional current. The motion of negatively-charged electrons around an electric circuit, one of the most familiar forms of current, is thus deemed positive in the opposite direction to that of the electrons.[26] However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation.
The process by which electric current passes through a material is termed electrical conduction, and its nature varies with that of the charged particles and the material through which they are travelling. Examples of electric currents include metallic conduction, where electrons flow through a conductor such as metal, and electrolysis, where ions (charged atoms) flow through liquids. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second,[16] the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires.[27]
Current causes several observable effects, which historically were the means of recognising its presence. That water could be decomposed by the current from a voltaic pile was discovered by Nicholson and Carlisle in 1800, a process now known as electrolysis. Their work was greatly expanded upon by Michael Faraday in 1833.[28] Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840.[28] One of the most important discoveries relating to current was made accidentally by Hans Christian Ørsted in 1820, when, while preparing a lecture, he witnessed the current in a wire disturbing the needle of a magnetic compass.[29] He had discovered electromagnetism, a fundamental interaction between electricity and magnetics.
In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how the current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative.[30] If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sinusoidal wave.[31] Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance.[32] These properties however can become important when circuitry is subjected to transients, such as when first energised.
Electric field
Main article: Electric field
See also: Electrostatics
The concept of the electric field was introduced by Michael Faraday. An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses, and like it, extends towards infinity and shows an inverse square relationship with distance.[21] However, there is an important difference. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Thus gravity is the dominant force at distance in the universe, despite being much weaker.[22]
An electric field generally varies in space,[33] and its strength at any one point is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point.[34] The conceptual charge, termed a 'test charge', must be vanishingly small to prevent its own electric field disturbing the main field and must also be stationary to prevent the effect of magnetic fields. As the electric field is defined in terms of force, and force is a vector, so it follows that an electric field is also a vector, having both magnitude and direction. Specifically, it is a vector field.[34]
The study of electric fields created by stationary charges is called electrostatics. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. This concept was introduced by Faraday,[35] whose term 'lines of force' still sometimes sees use. The field lines are the paths that a point positive charge would seek to make as it was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines.[35] Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves.[36]
A hollow conducting body carries all its charge on its outer surface. The field is therefore zero at all places inside the body.[37] This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects.
The principles of electrostatics are important when designing items of high-voltage equipment. There is a finite limit to the electric field strength that may be withstood by any medium. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts. Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Over larger gaps, its breakdown strength is weaker, perhaps 1 kV per centimetre.[38] The most visible natural occurrence of this is lightning, caused when charge becomes separated in the clouds by rising columns of air, and raises the electric field in the air to greater than it can withstand. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh.[39]
The field strength is greatly affected by nearby conducting objects, and it is particularly intense when it is forced to curve around sharply pointed objects. This principle is exploited in the lightning conductor, the sharp spike of which acts to encourage the lightning stroke to develop there, rather than to the building it serves to protect.[40]
Electric potential
Main article: Electric potential
See also: Voltage
The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity.[41] This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated.[41] The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage.
For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged – and unchargeable.[42]
Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field.[43] As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a conductor's surface, otherwise this would produce a force on the charge carriers and the electrons will stream out of the conductor.
The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest gradient of potential, and where the equipotentials lie closest together.[16]
Electromagnetism
Main article: Electromagnetism
Ørsted's discovery in 1821 that a magnetic field existed around all sides of a wire carrying an electric current indicated that there was a direct relationship between electricity and magnetism. Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. The force on the compass needle did not direct it to or away from the current-carrying wire, but acted at right angles to it.[29] Ørsted's slightly obscure words were that "the electric conflict acts in a revolving manner." The force also depended on the direction of the current, for if the flow was reversed, then the force did too.[44]
Ørsted did not fully understand his discovery, but he observed the effect was reciprocal: a current exerts a force on a magnet, and a magnetic field exerts a force on a current. The phenomenon was further investigated by Ampère, who discovered that two parallel current-carrying wires exerted a force upon each other: two wires conducting currents in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart.[45] The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.[45]
This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. Faraday's homopolar motor consisted of a permanent magnet sitting in a pool of mercury. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury. The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained.[46]
Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. Further analysis of this process, known as electromagnetic induction, enabled him to state the principle, now known as Faraday's law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop. Exploitation of this discovery enabled him to invent the first electrical generator in 1831, in which he converted the mechanical energy of a rotating copper disc to electrical energy.[46] Faraday's disc was inefficient and of no use as a practical generator, but it showed the possibility of generating electric power using magnetism, a possibility that would be taken up by those that followed on from his work.
Faraday's and Ampère's work showed that a time-varying magnetic field acted as a source of an electric field, and a time-varying electric field was a source of a magnetic field. Thus, when either field is changing in time, then a field of the other is necessarily induced.[47] Such a phenomenon has the properties of a wave, and is naturally referred to as an electromagnetic wave. Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. He could moreover prove that such a wave would necessarily travel at the speed of light, and thus light itself was a form of electromagnetic radiation. Maxwell's Laws, which unify light, fields, and charge are one of the great milestones of theoretical physics.[47]
Electric circuits
Main article: Electric circuit
An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task.
The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli.[48]
The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp.[48]
The capacitor is a device capable of storing charge, and thereby storing electrical energy in the resulting field. Conceptually, it consists of two conducting plates separated by a thin insulating layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current, but instead blocks it.[48]
The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second.[48] The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.
Production and uses
Generation and transmission
Main article: Electricity generation
See also: Electric power transmission and Mains power around the world
Thales' experiments with amber rods were the first studies into the production of electrical energy. While this method, now known as the triboelectric effect, is capable of lifting light objects and even generating sparks, it is extremely inefficient.[49] It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available. The voltaic pile, and its modern descendant, the electrical battery, store energy chemically and make it available on demand in the form of electrical energy.[49] The battery is a versatile and very common power source which is ideally suited to many applications, but its energy storage is finite, and once discharged it must be disposed of or recharged. For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines.
Electrical power is usually generated by electro-mechanical generators driven by steam produced from fossil fuel combustion, or the heat released from nuclear reactions; or from other sources such as kinetic energy extracted from wind or flowing water. The modern steam turbine invented by Sir Charles Parsons in 1884 today generates about 80 percent of the electric power in the world using a variety of heat sources. Such generators bear no resemblance to Faraday's homopolar disc generator of 1831, but they still rely on his electromagnetic principle that a conductor linking a changing magnetic field induces a potential difference across its ends.[50] The invention in the late nineteenth century of the transformer meant that electrical power could be transmitted more efficiently at a higher voltage but lower current. Efficient electrical transmission meant in turn that electricity could be generated at centralised power stations, where it benefited from economies of scale, and then be despatched relatively long distances to where it was needed.[51][52]
Since electrical energy cannot easily be stored in quantities large enough to meet demands on a national scale, at all times exactly as much must be produced as is required.[51] This requires electricity utilities to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. A certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses.
Demand for electricity grows with great rapidity as a nation modernises and its economy develops. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,[53] a rate of growth that is now being experienced by emerging economies such as those of India or China.[54][55] Historically, the growth rate for electricity demand has outstripped that for other forms of energy.[56]
Environmental concerns with electricity generation have led to an increased focus on generation from renewable sources, in particular from wind- and hydropower. While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean.[57]
Uses
Electricity is an extremely flexible form of energy, and has been adapted to a huge, and growing, number of uses.[58] The invention of a practical incandescent light bulb in the 1870s led to lighting becoming one of the first publicly available applications of electrical power. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories.[59] Public utilities were set up in many cities targeting the burgeoning market for electrical lighting.
The Joule heating effect employed in the light bulb also sees more direct use in electric heating. While this is versatile and controllable, it can be seen as wasteful, since most electrical generation has already required the production of heat at a power station.[60] A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings.[61] Electricity is however a highly practical energy source for refrigeration,[62] with air conditioning representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate.[63]
Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. With the construction of first intercontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. Optical fibre and satellite communication technology have taken a share of the market for communications systems, but electricity can be expected to remain an essential part of the process.
The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. A stationary motor such as a winch is easily provided with a supply of power, but a motor that moves with its application, such as an electric vehicle, is obliged to either carry along a power source such as a battery, or to collect current from a sliding contact such as a pantograph, placing restrictions on its range or performance.
Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century,[64] and a fundamental building block of all modern circuitry. A modern integrated circuit may contain several billion miniaturised transistors in a region only a few centimetres square.[65]
Electricity and the natural world
Physiological effects
Main article: Electric shock
A voltage applied to a human body causes an electric current through the tissues, and although the relationship is non-linear, the greater the voltage, the greater the current.[66] The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.1 mA to 1 mA for mains-frequency electricity, though a current as low as a microamp can be detected as an electrovibration effect under certain conditions.[67] If the current is sufficiently high, it will cause muscle contraction, fibrillation of the heart, and tissue burns.[66] The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of torture. Death caused by an electric shock is referred to as electrocution. Electrocution is still the means of judicial execution in some jurisdictions, though its use has become rarer in recent times.[68]
Electrical phenomena in nature
Electricity is not a human invention, and may be observed in several forms in nature, a prominent manifestation of which is lightning. Many interactions familiar at the macroscopic level, such as touch, friction or chemical bonding, are due to interactions between electric fields on the atomic scale. The Earth's magnetic field is thought to arise from a natural dynamo of circulating currents in the planet's core.[69] Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when subjected to external pressure.[70] This phenomenon is known as piezoelectricity, from the Greek piezein (πιέζειν), meaning to press, and was discovered in 1880 by Pierre and Jacques Curie. The effect is reciprocal, and when a piezoelectric material is subjected to an electric field, a small change in physical dimensions take place.[70]
Some organisms, such as sharks, are able to detect and respond to changes in electric fields, an ability known as electroreception,[71] while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon.[3] The order Gymnotiformes, of which the best known example is the electric eel, detect or stun their prey via high voltages generated from modified muscle cells called electrocytes.[3][4] All animals transmit information along their cell membranes with voltage pulses called action potentials, whose functions include communication by the nervous system between neurons and muscles.[72] An electric shock stimulates this system, and causes muscles to contract.[73] Action potentials are also responsible for coordinating activities in certain plants and mammals.[72]
Cultural perception
In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialised Western world. The popular culture of the time accordingly often depicts it as a mysterious, quasi-magical force that can slay the living, revive the dead or otherwise bend the laws of nature.[74] This attitude is manifest in Mary Shelley's Frankenstein (1819), which originated the cliché of a mad scientist reviving a patchwork creature with electrical power.
As the public familiarity with electricity as the lifeblood of the Second Industrial Revolution grew, its wielders were more often cast in a positive light,[75] such as the workers who "finger death at their gloves' end as they piece and repiece the living wires" in Rudyard Kipling's 1907 poem The Sons of Martha.[75] Electrically powered vehicles of every sort featured large in adventure stories such as those of Jules Verne or the Tom Swift books.[75] The masters of electricity, whether fictional or real—including scientists such as Thomas Edison, Charles Steinmetz or Nikola Tesla—were popularly conceived of as having wizard-like powers.[75]
With electricity ceasing to be a novelty and becoming a necessity of everyday life in the later half of the 20th century, it required particular attention by popular culture only when it stops flowing,[75] an event that usually signals disaster.[75] The people who keep it flowing, such as the nameless hero of Jimmy Webb’s song "Wichita Lineman" (1968),[75] are still often cast as heroic, wizard-like figures.[75]
See also
- Ampere's rule, connects the direction of an electric current and its associated magnetic currents.
- Electrical energy, the potential energy of a system of charges
- Electricity market, the sale of electrical energy
- Electrical phenomena, observable events which illuminate the physical principles of electricity
- Electric power, the rate at which electrical energy is transferred
- Electronics, the study of the movement of charge through certain materials and devices
- Hydraulic analogy, an analogy between the flow of water and electric current
- Mains electricity, the AC electric power supply
- Mains power systems, includes a list of countries and territories, with the plugs, voltages and frequencies they use
- Native American contributions#E Moche electricity
Notes
a. ^ the New Latin ēlectricus, "amber-like", came from from the classical Latin electrum, itself coming from the Greek ἤλεκτρον, (elektron), meaning amber
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External links
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| Misspellings: electricity |
Common misspelling(s) of electricity
- electricty
| Translations: Electricity |
Dansk (Danish)
n. - elektricitet, elektricitetslære, elektrisk strøm
Nederlands (Dutch)
elektriciteit, gespannenheid, opwinding, elektriciteitsleer
Français (French)
n. - électricité, (fig) courant
Deutsch (German)
n. - Elektrizität, Strom
Ελληνική (Greek)
n. - (φυσ.) ηλεκτρισμός, ηλεκτρική ενέργεια, ηλεκτρικό ρεύμα ή φορτίο
Italiano (Italian)
elettricità, corrente
Português (Portuguese)
n. - eletricidade (f)
Русский (Russian)
электричество, электрический ток
Español (Spanish)
n. - electricidad, tensión
Svenska (Swedish)
n. - elektricitet, ström
中文（简体）(Chinese (Simplified))
电, 电学, 电流
中文（繁體）(Chinese (Traditional))
n. - 電, 電學, 電流
العربيه (Arabic)
(الاسم) كهرباء
עברית (Hebrew)
n. - חשמל, התרגשות רבה
If you are unable to view some languages clearly, click here.
To select your translation preferences click here.
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