Electricity - Electricity
Electricity - Electricity





About Electricity - Electricity

"Revitalization" or resuscitation of apparently dead or drowned persons was reported in the medical literature shortly after Galvani's work.
(1991), "Electrical engineering: the backbone of society", Proceedings of the IEE: Science, Measurement and Technology 138 (1): 1–10, doi:10. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp. 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 certain amount of generation must always be held in reserve to cushion an electrical grid against inevitable disturbances and losses. A current was allowed through a wire suspended from a pivot above the magnet and dipped into the mercury.
A history of electricity (The intellectual rise in electricity) from antiquity to the days of Benjamin Franklin. A modern integrated circuit may contain several billion miniaturised transistors in a region only a few centimetres square. 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. 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. 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.
Air, for example, tends to arc across small gaps at electric field strengths which exceed 30 kV per centimetre. Alternating current is affected by electrical properties that are not observed under steady state direct current, such as inductance and capacitance. Alternating current is any current that reverses direction repeatedly; almost always this takes the form of a sine wave. Although electrification brought with it its own dangers, replacing the naked flames of gas lighting greatly reduced fire hazards within homes and factories. 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.
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. An exception is the electric field surrounding a planar conductor of infinite extent, the field of which is uniform. 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. 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. Beyond this point, electrical breakdown occurs and an electric arc causes flashover between the charged parts.
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. Charge is possessed not just by matter, but also by antimatter, each antiparticle bearing an equal and opposite charge to its corresponding particle. Charge originates in the atom, in which its most familiar carriers are the electron and proton. Conceptually, it consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. Current can consist of any moving charged particles; most commonly these are electrons, but any charge in motion constitutes a current.
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. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable. 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. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Electrical power is the backbone of modern industrial society, and is expected to remain so for the foreseeable future.
Electricity gives a wide variety of well-known electrical effects, such as lightning, static electricity, electromagnetic induction and the flow of electrical current in an electrical wire. Electricity's extraordinary versatility as a means of providing energy means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrocution is still the means of judicial execution in some jurisdictions, though its use has become rarer in recent times. 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. 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.
For large electrical demands electrical energy must be generated and transmitted continuously over conductive transmission lines. 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. Gravity always acts in attraction, drawing two masses together, while the electric field can result in either attraction or repulsion. 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. 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.
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. 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. In a loose but common use of the term, "electricity" may be used to mean "wired for electricity" which means a working connection to an electric power station. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. 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.
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. 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. 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. Maxwell developed a set of equations that could unambiguously describe the interrelationship between electric field, magnetic field, electric charge, and electric current. Maxwell's Laws, which unify light, fields, and charge are one of the great milestones of theoretical physics.
Moreover, the interaction seemed different from gravitational and electrostatic forces, the two forces of nature then known. 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. 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. 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. 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.
Since large bodies such as planets generally carry no net charge, the electric field at a distance is usually zero. Such a connection grants the user of "electricity" access to the electric field present in electrical wiring, and thus to electric power. 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. 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. 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.
The Earth's magnetic field is thought to arise from a natural dynamo of circulating currents in the planet's core. The Q originally stood for 'quantity of electricity', the term 'electricity' now more commonly expressed as 'charge'. The United States showed a 12% increase in demand during each year of the first three decades of the twentieth century,[55] a rate of growth that is now being experienced by emerging economies such as those of India or China. The effect is reciprocal, and when a piezoelectric material is subjected to an electric field, a small change in physical dimensions take place. 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.
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. 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. The field may be visualised by a set of imaginary lines whose direction at any point is the same as that of the field. 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. The level of electromagnetic emissions generated by electric arcing is high enough to produce electromagnetic interference, which can be detrimental to the workings of adjacent equipment.
The magnet exerted a tangential force on the wire, making it circle around the magnet for as long as the current was maintained. 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. 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. 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. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω.
The pain caused by an electric shock can be intense, leading electricity at times to be employed as a method of torture. 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. 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. 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. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'.
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. The time-averaged value of an alternating current is zero, but it delivers energy in first one direction, and then the reverse. 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. The voltage of a large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. The voltage source V on the left drives a current I around the circuit, delivering electrical energy into the resistor R.
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. There is a finite limit to the electric field strength that may be withstood by any medium. These phenomena were investigated in the late eighteenth century by Charles-Augustin de Coulomb, who deduced that charge manifests itself in two opposing forms. These results were known to Mary Shelley when she authored Frankenstein (1819), although she does not name the method of revitalization of the monster. They must also lie parallel to a conductor's surface, otherwise this would produce a force that will move the charge carriers to even the potential of the surface.
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. Through such people as Nikola Tesla, Galileo Ferraris, Oliver Heaviside, Thomas Edison, Ottó Bláthy, Ányos Jedlik, Sir Charles Parsons, Joseph Swan, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution. Thus, when either field is changing in time, then a field of the other is necessarily induced. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor.
While debate can be expected to continue over the environmental impact of different means of electricity production, its final form is relatively clean. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of a millimetre per second,[17] the electric field that drives them itself propagates at close to the speed of light, enabling electrical signals to pass rapidly along wires. 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. 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. While this method, now known as the triboelectric effect, is capable of lifting light objects and even generating sparks, it is extremely inefficient.
With the construction of first intercontinental, and then transatlantic, telegraph systems in the 1860s, electricity had enabled communications in minutes across the globe. ^ the New Latin ēlectricus, "amber-like", came from the classical Latin electrum, itself coming from the Greek ἤλεκτρον, (elektron), meaning amber " The force also depended on the direction of the current, for if the flow was reversed, then the force did too.  92–94, ISBN 0-89526-163-4  It is uncertain if Franklin personally carried out this experiment, but it is popularly attributed to him. 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.
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. 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. An electric field generally varies in space,[35] 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. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. 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,[78] 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 Sons of Martha.
Benjamin Franklin conducted extensive research on electricity in the 18th century, as documented by Joseph Priestley (1767) History and Present Status of Electricity, with whom Franklin carried on extended correspondence. 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. 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. 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. Electrical phenomena have been studied since antiquity, though advances in the science were not made until the seventeenth and eighteenth centuries.
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. Electricity is not a human invention, and may be observed in several forms in nature, a prominent manifestation of which is lightning. Electricity is the science, engineering, technology and physical phenomena associated with the presence and flow of electric charges. Electricity is used within telecommunications, and indeed the electrical telegraph, demonstrated commercially in 1837 by Cooke and Wheatstone, was one of its earliest applications. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.
Electronic devices make use of the transistor, perhaps one of the most important inventions of the twentieth century,[66] and a fundamental building block of all modern circuitry. Environmental concerns with electricity generation have led to an increased focus on generation from renewable sources, in particular from wind and hydropower. Experimentation by Faraday in 1831 revealed that a wire moving perpendicular to a magnetic field developed a potential difference between its ends. 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. For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared.
In 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). In the 19th and early 20th century, electricity was not part of the everyday life of many people, even in the industrialised Western world. Mains electricity by country, includes a list of countries and territories, with the plugs, voltages and frequencies they use 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.
Some organisms, such as sharks, are able to detect and respond to changes in electric fields, an ability known as electroreception,[74] while others, termed electrogenic, are able to generate voltages themselves to serve as a predatory or defensive weapon. The Joule heating effect employed in the light bulb also sees more direct use in electric heating. The capacitor is a development of the Leyden jar and is a device capable of storing charge, and thereby storing electrical energy in the resulting field. The charge on electrons and protons is opposite in sign, hence an amount of charge may be expressed as being either negative or positive. The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics.
The effects of electromagnetism are most visibly employed in the electric motor, which provides a clean and efficient means of motive power. 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. The electric motor exploits an important effect of electromagnetism: a current through a magnetic field experiences a force at right angles to both the field and current 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. 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 inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. The light bulb, an early application of electricity, operates by Joule heating: the passage of current through resistance generating heat The movement of electric charge is known as an electric current, the intensity of which is usually measured in amperes. 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. 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.
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 use of electricity gives a very convenient way to transfer energy, and because of this it has been adapted to a huge, and growing, number of uses. The word electricity is from the New Latin ēlectricus, "amber-like"[a], coined in the year 1600 from the Greek ήλεκτρον (electron) meaning amber, because electrical effects were produced classically by rubbing amber. This relationship between magnetic fields and currents is extremely important, for it led to Michael Faraday's invention of the electric motor in 1821. 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.
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,[78] an event that usually signals disaster. [11] A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. [12] He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge. [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] Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and 1862.
[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. [16] Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire. [17] 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. [18] 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. [19][20] The electromagnetic force is very strong, second only in strength to the strong interaction,[21] but unlike that force it operates over all distances.
[22] 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. [24] The amount of charge is usually given the symbol Q and expressed in coulombs;[25] each electron carries the same charge of approximately −1. [27] 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. [29] Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. [29] 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.
[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. [32] If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. [33] Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. [34] These properties however can become important when circuitry is subjected to transients, such as when first energised. [36] 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.
[37] 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. [39] This is the operating principal of the Faraday cage, a conducting metal shell which isolates its interior from outside electrical effects. [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. [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.
[40] 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. [43] 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. [43] 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. [45] 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. [47] The interaction is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere.
[48] 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. [49] Such a phenomenon has the properties of a wave, and is naturally referred to as an electromagnetic wave. [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. [50] 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. [51] It was not until the invention of the voltaic pile in the eighteenth century that a viable source of electricity became available.
[51] 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. [52] 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. [53] This requires electricity utilities to make careful predictions of their electrical loads, and maintain constant co-ordination with their power stations. [56][57] Historically, the growth rate for electricity demand has outstripped that for other forms of energy. [60] 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.
[61] Public utilities were set up in many cities targeting the burgeoning market for electrical lighting. [62] A number of countries, such as Denmark, have issued legislation restricting or banning the use of electric heating in new buildings. [63] Electricity is however a highly practical energy source for refrigeration,[64] with air conditioning representing a growing sector for electricity demand, the effects of which electricity utilities are increasingly obliged to accommodate. [69] The lack of any visible sign that a conductor is electrified makes electricity a particular hazard. [69] The threshold for perception varies with the supply frequency and with the path of the current, but is about 0.
[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. [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. [70] If the current is sufficiently high, it will cause muscle contraction, fibrillation of the heart, and tissue burns. [72] Certain crystals, such as quartz, or even sugar, generate a potential difference across their faces when subjected to external pressure. [73] This phenomenon is known as piezoelectricity, from the Greek piezein (πιέζειν), meaning to press, and was discovered in 1880 by Pierre and Jacques Curie.
[77] This attitude began with the 1771 experiments of Luigi Galvani in which the legs of dead frogs were shown to twitch on application of animal electricity. [78] Electrically powered vehicles of every sort featured large in adventure stories such as those of Jules Verne and the Tom Swift books. [78] 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. [78] The people who keep it flowing, such as the nameless hero of Jimmy Webb’s song "Wichita Lineman" (1968),[78] are still often cast as heroic, wizard-like figures. [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.
^ "The repulsive force between two small spheres charged with the same type of electricity is inversely proportional to the square of the distance between the centres of the two spheres. ^ Berkson, William (1974) Fields of force: the development of a world view from Faraday to Einstein p. ^ Carbon Sequestration Leadership Forum, An Energy Summary of India, archived from the original on 2007-12-05, http://web. ^ Chalmers, Gordon (1937), "The Lodestone and the Understanding of Matter in Seventeenth Century England", Philosophy of Science 4 (1): 75–95, doi:10. ^ Close, Frank (2007), The New Cosmic Onion: Quarks and the Nature of the Universe, CRC Press, p.
^ Edison Electric Institute, History of the Electric Power Industry, archived from the original on November 13, 2007, http://web. ^ Moller, Peter; Kramer, Bernd (December 1991), "Review: Electric Fish", BioScience (American Institute of Biological Sciences) 41 (11): 794–6 [794], doi:10. ^ ReVelle, Charles and Penelope (1992), The Global Environment: Securing a Sustainable Future, Jones & Bartlett, p. ^ Saeli, Sue; MacIsaac, Dan (2007), "Using Gravitational Analogies To Introduce Elementary Electrical Field Theory Concepts", The Physics Teacher 45 (2): 104, Bibcode 2007PhTea. ^ Shectman, Jonathan (2003), Groundbreaking Scientific Experiments, Inventions, and Discoveries of the 18th Century, Greenwood Press, pp.
^ Trefil, James (2003), The Nature of Science: An A–Z Guide to the Laws and Principles Governing Our Universe, Houghton Mifflin Books, p. ^ Wald, Matthew (21 March 1990), "Growing Use of Electricity Raises Questions on Supply", New York Times, http://query. ^ a b Berkson, William (1974), Fields of Force: The Development of a World View from Faraday to Einstein, Routledge, p. ^ a b Dell, Ronald; Rand, David (2001), "Understanding Batteries", Unknown (Royal Society of Chemistry) 86: 2–4, Bibcode 1985STIN. electric field (see electrostatics): an especially simple type of electromagnetic field produced by an electric charge even when it is not moving (i.
electric potential: the capacity of an electric field to do work on an electric charge, typically measured in volts. electric power (which can refer imprecisely to a quantity of electrical potential energy or else more correctly to electrical energy per time) that is provided commercially, by the electrical power industry. electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. 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. 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.