78-522: Rajasthan Rajya Vidyut Utpadan Nigam Ltd ( RVUNL ) is the electricity generation company of the Government of Rajasthan state in India . Rajasthan Rajya Vidyut Utpadan Nigam Ltd has been entrusted with the job of development of power projects under state sector, in the state along with operation and maintenance of state-owned power stations by un-bundling the erstwhile RSEB. The Government of Rajasthan continued
156-455: A conductor 's surface, since otherwise there would be a force along the surface of the conductor that would move the charge carriers to even the potential across the surface. 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,
234-461: A force on each other, an effect that was known, though not understood, in antiquity. A lightweight ball suspended by a fine thread 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
312-737: A magnetic field . In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts . Electricity plays a central role in many modern technologies, serving in electric power where electric current is used to energise equipment, and in electronics dealing with electrical circuits involving active components such as vacuum tubes , transistors , diodes and integrated circuits , and associated passive interconnection technologies. The study of electrical phenomena dates back to antiquity, with theoretical understanding progressing slowly until
390-409: A steady state current, but instead blocks it. 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
468-432: A charge of Q coulombs every t seconds passing through an electric potential ( voltage ) difference of V is where Electric power is generally supplied to businesses and homes by the electric power industry . Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters , which keep
546-512: A common reference point to which potentials may be expressed and compared is useful. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground . Earth is assumed to be an infinite source of equal amounts of positive and negative charge and is therefore electrically uncharged—and unchargeable. Electric potential
624-468: A current of one amp. The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. 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 . The unit of capacitance
702-490: A dampened kite string and flown the kite in a storm-threatened sky . A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature. He also explained the apparently paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1775, Hugh Williamson reported
780-420: A group of rays , flattened cartilaginous fish with enlarged pectoral fins , composing the order Torpediniformes / t ɔːr ˈ p ɛ d ɪ n ɪ f ɔːr m iː z / . They are known for being capable of producing an electric discharge , ranging from 8 to 220 volts , depending on species, used to stun prey and for defense. There are 69 species in four families. Perhaps the best known members are those of
858-425: A large lightning cloud may be as high as 100 MV and have discharge energies as great as 250 kWh. 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 strike to develop there, rather than to
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#1732880857827936-399: A manner similar to the way the torpedo fish stuns with electricity. Scribonius Largus , a Roman physician, recorded the use of torpedo fish for treatment of headaches and gout in his Compositiones Medicae of 46 AD. In the 1770s the electric organs of the torpedo ray were the subject of Royal Society papers by John Walsh , and John Hunter . These appear to have influenced
1014-402: A millimetre per second, the electric field that drives them itself propagates at close to the speed of light , enabling electrical signals to pass rapidly along wires. 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,
1092-553: A more reliable source of electrical energy than the electrostatic machines previously used. 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. 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. While
1170-610: A parallel circuit, whereas freshwater batteries are arranged in series. This allows freshwater rays to transmit discharges of higher voltage, as freshwater cannot conduct electricity as well as saltwater. With such a battery, an electric ray may electrocute larger prey with a voltage of between 8 volts in some narcinids to 220 volts in Torpedo nobiliana , the Atlantic torpedo. The 60 or so species of electric rays are grouped into 12 genera and two families. The Narkinae are sometimes elevated to
1248-425: 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
1326-891: 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. 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. The resistor
1404-406: A process now known as electrolysis . Their work was greatly expanded upon by Michael Faraday in 1833. Current through a resistance causes localised heating, an effect James Prescott Joule studied mathematically in 1840. 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
1482-471: A rapidly changing one. Electric power is the rate at which electric energy is transferred by an electric circuit . The SI unit of power is the watt , one joule per second . Electric power, like mechanical power , is the rate of doing work , measured in watts , and represented by the letter P . The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of
1560-485: 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
1638-595: A running total of the electric energy delivered to a customer. Unlike fossil fuels , electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes , transistors , diodes , sensors and integrated circuits , and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes digital switching possible, and electronics
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#17328808578271716-431: A scientific curiosity into an essential tool for modern life. In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to
1794-568: A series of experiments to the Royal Society on the shocks delivered by the electric eel ; that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs . In 1791, Luigi Galvani published his discovery of bioelectromagnetics , demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta 's battery, or voltaic pile , of 1800, made from alternating layers of zinc and copper, provided scientists with
1872-510: A series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic , in contrast to minerals such as magnetite , which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating , based on
1950-485: 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 in a vacuum such a wave would travel at the speed of light , and thus light itself was a form of electromagnetic radiation. Maxwell's equations , which unify light, fields, and charge are one of the great milestones of theoretical physics. Electric ray see text The electric rays are
2028-477: A solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect. In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons , and as positively charged electron deficiencies called holes . These charges and holes are understood in terms of quantum physics. The building material
2106-511: A wire disturbing the needle of a magnetic compass. He had discovered electromagnetism , a fundamental interaction between electricity and magnetics. 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. In engineering or household applications, current is often described as being either direct current (DC) or alternating current (AC). These terms refer to how
2184-448: 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. 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
2262-402: A wire. 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. 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
2340-584: 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. 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
2418-411: Is a vector field . 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, 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
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2496-452: 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. An electric field generally varies in space, and its strength at any one point
2574-401: 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 . The force acts on
2652-468: Is defined as negative, and that by protons is positive. Before these particles were discovered, Benjamin Franklin had defined a positive charge as being the charge acquired by a glass rod when it is rubbed with a silk cloth. A proton by definition carries a charge of exactly 1.602 176 634 × 10 coulombs . This value is also defined as the elementary charge . No object can have a charge smaller than
2730-483: Is defined as the force (per unit charge) that would be felt by a stationary, negligible charge if placed at that point. 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 , having both magnitude and direction , it follows that an electric field
2808-531: Is integral to applications spanning transport , heating , lighting , communications , and computation , making it the foundation of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish . Ancient Egyptian texts dating from 2750 BCE described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek , Roman and Arabic naturalists and physicians . Several ancient writers, such as Pliny
2886-406: Is mediated by the magnetic field each current produces and forms the basis for the international definition of the ampere . 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
2964-415: Is most often a crystalline semiconductor . Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium -based point-contact transistor , was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947, followed by the bipolar junction transistor in 1948. By modern convention, the charge carried by electrons
3042-403: 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
3120-436: Is related to magnetism , both being part of the phenomenon of electromagnetism , as described by Maxwell's equations . Common phenomena are related to electricity, including lightning , static electricity , electric heating , electric discharges and many others. The presence of either a positive or negative electric charge produces an electric field . The motion of electric charges is an electric current and produces
3198-531: Is subjected to transients , such as when first energised. The concept of the electric field was introduced by Michael Faraday . An electric field is created by a charged body in the space that surrounds it, and results in a force exerted on any other charges placed within the field. The electric field acts between two charges in a similar manner to the way that the gravitational field acts between two masses , and like it, extends towards infinity and shows an inverse square relationship with distance. However, there
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3276-406: 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. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes
3354-415: 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
3432-524: Is therefore 0 at all places inside the body. 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
3510-682: Is thick and flabby, with soft loose skin with no dermal denticles or thorns. A pair of kidney -shaped electric organs are at the base of the pectoral fins. The snout is broad, large in the Narcinidae, but reduced in all other families. The mouth, nostrils , and five pairs of gill slits are underneath the disc. Electric rays are found from shallow coastal waters down to at least 1,000 m (3,300 ft) deep. They are sluggish and slow-moving, propelling themselves with their tails, not by using their pectoral fins as other rays do. They feed on invertebrates and small fish. They lie in wait for prey below
3588-409: Is usually measured in volts , and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity. This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference , and is the energy required to move a unit charge between two specified points. An electric field has
3666-536: Is widely used in information processing , telecommunications , and signal processing . Interconnection technologies such as circuit boards , electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system . Today, most electronic devices use semiconductor components to perform electron control. The underlying principles that explain how semiconductors work are studied in solid state physics , whereas
3744-700: The Neo-Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron , the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne 's Pseudodoxia Epidemica of 1646. Isaac Newton made early investigations into electricity, with an idea of his written down in his book Opticks arguably
3822-423: The electromagnetic force , one of the four fundamental forces of nature. Experiment has shown charge to be a conserved quantity , that is, the net charge within an electrically isolated system will always remain constant regardless of any changes taking place within that system. Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as
3900-476: The genus Torpedo . The torpedo undersea weapon is named after it. The name comes from the Latin torpere , 'to be stiffened or paralyzed', from the effect on someone who touches the fish. Electric rays have a rounded pectoral disc with two moderately large rounded-angular (not pointed or hooked) dorsal fins (reduced in some Narcinidae ), and a stout muscular tail with a well-developed caudal fin . The body
3978-511: The quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect". The photoelectric effect is also employed in photocells such as can be found in solar panels . The first solid-state device was the " cat's-whisker detector " first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with
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#17328808578274056-452: The strong interaction , but unlike that force it operates over all distances. In comparison with the much weaker gravitational force , the electromagnetic force pushing two electrons apart is 10 times that of the gravitational attraction pulling them together. Charge originates from certain types of subatomic particles , the most familiar carriers of which are the electron and proton . Electric charge gives rise to and interacts with
4134-529: The 17th and 18th centuries. The development of the theory of electromagnetism in the 19th century marked significant progress, leading to electricity's industrial and residential application by electrical engineers by the century's end. This rapid expansion in electrical technology at the time was the driving force behind the Second Industrial Revolution , with electricity's versatility driving transformations in both industry and society. Electricity
4212-538: The 1936 discovery of the Baghdad Battery , which resembles a galvanic cell , though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete , in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined
4290-645: The Elder and Scribonius Largus , attested to the numbing effect of electric shocks delivered by electric catfish and electric rays , and knew that such shocks could travel along conducting objects. Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. 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. Thales of Miletus made
4368-527: The RVUNL under the companies Act 1956 on 19 July 2000. The nigam is playing lead role in giving high priority to the power generation and manifold and rapid development of the state. The chairman and managing director is Shri P. Ramesh. The installed capacity of RVUNL was as of December 2018 is 6831 MW. Electricity Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge . Electricity
4446-408: The beginning of the field theory of the electric force. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke , Robert Boyle , Stephen Gray and C. F. du Fay . Later 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
4524-419: The building it serves to protect. 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
4602-426: 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. The electromagnetic force is very strong, second only in strength to
4680-450: 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. 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
4758-411: The current varies in time. Direct current, as produced by example from a battery and required by most electronic devices, is a unidirectional flow from the positive part of a circuit to the negative. If, as is most common, this flow is carried by electrons, they will be travelling in the opposite direction. Alternating current is any current that reverses direction repeatedly; almost always this takes
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#17328808578274836-516: The design and construction of electronic circuits to solve practical problems are part of electronics engineering . Faraday's and Ampère's work showed that a time-varying magnetic field created an electric field, and a time-varying electric field created a magnetic field. Thus, when either field is changing in time, a field of the other is always induced. These variations are an electromagnetic wave . Electromagnetic waves were analysed theoretically by James Clerk Maxwell in 1864. Maxwell developed
4914-478: The early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering . Through such people as Alexander Graham Bell , Ottó Bláthy , Thomas Edison , Galileo Ferraris , Oliver Heaviside , Ányos Jedlik , William Thomson, 1st Baron Kelvin , Charles Algernon Parsons , Werner von Siemens , Joseph Swan , Reginald Fessenden , Nikola Tesla and George Westinghouse , electricity turned from
4992-427: 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. The interaction
5070-448: The electronic electrometer . 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. Electric current can flow through some things, electrical conductors , but will not flow through an electrical insulator . By historical convention,
5148-416: The electrons. However, depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once. The positive-to-negative convention is widely used to simplify this situation. 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
5226-428: The elementary charge, and any amount of charge an object may carry is a multiple of the elementary charge. An electron has an equal negative charge, i.e. −1.602 176 634 × 10 coulombs . Charge is possessed not just by matter , but also by antimatter , each antiparticle bearing an equal and opposite charge to its corresponding particle. The presence of charge gives rise to an electrostatic force: charges exert
5304-495: The form of a sine wave . Alternating current thus pulses back and forth within a conductor without the charge moving any net distance over time. 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 . These properties however can become important when circuitry
5382-441: The lower to the upper surface of the body. The nerves that signal the organ to discharge branch repeatedly, then attach to the lower side of each plaque in the batteries. These are composed of hexagonal columns, closely packed in a honeycomb formation. Each column consists of 500 to more than 1000 plaques of modified striated muscle, adapted from the branchial (gill arch) muscles. In marine fish , these batteries are connected as
5460-400: 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, or through plasmas such as electrical sparks. While the particles themselves can move quite slowly, sometimes with an average drift velocity only fractions of
5538-428: 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. Faraday's disc was inefficient and of no use as
5616-415: The sand or other substrate, using their electricity to stun and capture it. The electrogenic properties of electric rays have been known since antiquity, although their nature was not understood. The ancient Greeks used electric rays to numb the pain of childbirth and operations. In his dialogue Meno , Plato has the character Meno accuse Socrates of "stunning" people with his puzzling questions, in
5694-454: 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. 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, defining
5772-468: The thinking of Luigi Galvani and Alessandro Volta – the founders of electrophysiology and electrochemistry. Henry Cavendish proposed that electric rays use electricity; he built an artificial ray consisting of fish shaped Leyden jars to successfully mimic their behaviour in 1773. The torpedo fish, or electric ray, appears continuously in premodern natural histories as a magical creature, and its ability to numb fishermen without seeming to touch them
5850-418: 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. Ørsted's 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. Ørsted did not fully understand his discovery, but he observed
5928-417: The vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together. 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,
6006-423: Was a significant source of evidence for the belief in occult qualities in nature during the ages before the discovery of electricity as an explanatory mode. The electric rays have specialised electric organs . Many species of rays and skates outside the family have electric organs in the tail; however, the electric ray has two large kidney-shaped electric organs on each side of its head, where current passes from
6084-543: Was forced to move within the field; they are however an imaginary concept with no physical existence, and the field permeates all the intervening space between the lines. Field lines emanating from stationary charges have several key properties: first, that they originate at positive charges and terminate at negative charges; second, that they must enter any good conductor at right angles, and third, that they may never cross nor close in on themselves. A hollow conducting body carries all its charge on its outer surface. The field
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