who discovered the heating effect of electric current
James Prescott Joule
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Joule heating Joule heating, also known as Ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor produces heat. Joule's first law, also known as the Joule–Lenz law, states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current: Joule heating affects the whole electric conductor, unlike the Peltier effect which transfers heat from one electrical junction to another. James Prescott Joule first published in December 1840, an abstract in the "Proceedings of the Royal Society", suggesting
Joule heating
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Joule effect Joule effect and Joule's law are any of several different physical effects discovered or characterized by English physicist James Prescott Joule. These physical effects are not the same, but all are frequently or occasionally referred to in literature as the "Joule effect" or "Joule law" These physical effects include: Between the years 1840 and 1843 Joule made a careful study of the heat produced by an electric current. From this study, he developed Joule's laws of heating, the first of which is commonly referred to as the "Joule effect". Joule's first law expresses the relationship between heat generated
Joule effect
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Joule heating Joule heating, also known as Ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor produces heat. Joule's first law, also known as the Joule–Lenz law, states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current: Joule heating affects the whole electric conductor, unlike the Peltier effect which transfers heat from one electrical junction to another. James Prescott Joule first published in December 1840, an abstract in the "Proceedings of the Royal Society", suggesting
Joule heating
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Joule heating Joule heating, also known as Ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor produces heat. Joule's first law, also known as the Joule–Lenz law, states that the power of heating generated by an electrical conductor is proportional to the product of its resistance and the square of the current: Joule heating affects the whole electric conductor, unlike the Peltier effect which transfers heat from one electrical junction to another. James Prescott Joule first published in December 1840, an abstract in the "Proceedings of the Royal Society", suggesting
Joule heating
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with an average drift velocity only fractions of 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, 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
Electricity
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frequency, Kramers–Kronig relations, etc.) Resistors (and other elements with resistance) oppose the flow of electric current; therefore, electrical energy is required to push current through the resistance. This electrical energy is dissipated, heating the resistor in the process. This is called "Joule heating" (after James Prescott Joule), also called "ohmic heating" or "resistive heating". The dissipation of electrical energy is often undesired, particularly in the case of transmission losses in power lines. High voltage transmission helps reduce the losses by reducing the current for a given power. On the other hand, Joule heating is sometimes useful, for example in electric
Electrical resistance and conductance
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flow of holes within metals and semiconductors. Current can be measured using an ammeter. At the circuit level, various techniques are used to measure current: Joule heating, also known as "ohmic heating" and "resistive heating", is the process by which the passage of an electric current through a conductor produces heat. It was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current through the wire for a 30 minute period. By varying the current and the length of the
Electric current
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generation. Thermoelectric materials Thermoelectric materials show the thermoelectric effect in a strong or convenient form. The "thermoelectric effect" refers to phenomena by which either a temperature difference creates an electric potential or an electric potential creates a temperature difference. These phenomena are known more specifically as the Seebeck effect (converting temperature to current), Peltier effect (converting current to temperature), and Thomson effect (conductor heating/cooling). While all materials have a nonzero thermoelectric effect, in most materials it is too small to be useful. However, low-cost materials that have a sufficiently strong thermoelectric effect (and other required properties) could be used in
Thermoelectric materials
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Thermoelectric materials Thermoelectric materials show the thermoelectric effect in a strong or convenient form. The "thermoelectric effect" refers to phenomena by which either a temperature difference creates an electric potential or an electric potential creates a temperature difference. These phenomena are known more specifically as the Seebeck effect (converting temperature to current), Peltier effect (converting current to temperature), and Thomson effect (conductor heating/cooling). While all materials have a nonzero thermoelectric effect, in most materials it is too small to be useful. However, low-cost materials that have a sufficiently strong thermoelectric effect (and other required properties) could be used in applications
Thermoelectric materials
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Heating element A heating element converts electrical energy into heat through the process of resistive or Joule heating. Electric current passing through the element encounters resistance, resulting in heating of the element. Unlike the Peltier effect, this process is independent of the direction of current flow. Resistive heaters can be made of conducting PTC rubber materials where the resistivity increases exponentially with increasing temperature. Such a heater will produce high power when it is cold, and rapidly heat up itself to a constant temperature. Due to the exponentially increasing resistivity, the heater can never heat itself to warmer than this
Heating element
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Electric heating Electric heating is a process in which electrical energy is converted to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating: an electric current passing through a resistor will convert that electrical energy into heat energy. Most modern electric heating devices use nichrome wire as the active element; the heating element, depicted on the right, uses nichrome wire supported by ceramic
Electric heating
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Galvanism In biology, galvanism is the contraction of a muscle that is stimulated by an electric current. In physics and chemistry, it is the induction of electrical current from a chemical reaction, typically between two chemicals with differing electronegativities. The effect was named after the scientist Luigi Galvani, who investigated the effect of electricity on dissected animals in the 1780s and 1790s. In 1786, he discovered that, when a frog's legs are touched by both a copper probe and a piece of iron at the same time, they then twitch just as if an electric current were present. He originally
Galvanism
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electric energy. The photovoltaic effect can also occur when two photons are absorbed simultaneously in a process called two-photon photovoltaic effect... The photovoltaic effect was first observed by French physicist A. E. Becquerel in 1839. He explained his discovery in "Comptes rendus de l'Académie des sciences", "the production of an electric current when two plates of platinum or gold immersed in an acid, neutral, or alkaline solution are exposed in an uneven way to solar radiation." Besides the direct excitation of free electrons, a photovoltaic effect can also arise simply due to the heating caused by absorption of the light.
Photovoltaic effect
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Wiedemann effect The twisting of a ferromagnetic rod through which an electric current is flowing when the rod is placed in a longitudinal magnetic field. It was discovered by the German physicist Gustav Wiedemann in 1858 . The Wiedemann effect is one of the manifestations of magnetostriction in a field formed by the combination of a longitudinal magnetic field and a circular magnetic field that is created by an electric current. If the electric current (or the magnetic field) is alternating, the rod will begin torsional oscillation. In linear approach angle of rod torsion "α" does not depend on its
Wiedemann effect
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disturbances. In order to avoid this the wire is connected to a mechanical damper that end. Wiedemann effect The twisting of a ferromagnetic rod through which an electric current is flowing when the rod is placed in a longitudinal magnetic field. It was discovered by the German physicist Gustav Wiedemann in 1858 . The Wiedemann effect is one of the manifestations of magnetostriction in a field formed by the combination of a longitudinal magnetic field and a circular magnetic field that is created by an electric current. If the electric current (or the magnetic field) is alternating, the rod will
Wiedemann effect
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The heating leads to an increase in temperature, which is accompanied by temperature gradients. These thermal gradients in turn may generate a voltage through the Seebeck effect. Whether direct excitation or thermal effects dominate the photovoltaic effect will depend on many material parameters. In most photovoltaic applications the radiation is sunlight, and the devices are called solar cells. In the case of a p-n junction solar cell, illuminating the material creates an electric current as excited electrons and the remaining holes are swept in different directions by the built-in electric field of the depletion region. Photovoltaic effect The photovoltaic effect
Photovoltaic effect
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Hall effect The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was discovered by Edwin Hall in 1879. For clarity, the original effect is sometimes called the ordinary Hall effect to distinguish it from other "Hall effects" which have different physical mechanisms. The Hall coefficient is defined as the ratio of the induced electric field to the product of the current density and the applied magnetic field. It is a characteristic of the
Hall effect
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heat that is generated whenever a current is passed through a resistive material, is related, though it is not generally termed a thermoelectric effect. The Peltier–Seebeck and Thomson effects are thermodynamically reversible, whereas Joule heating is not. The Seebeck effect is the conversion of heat directly into electricity at the junction of different types of wire. Originally discovered in 1794 by Italian scientist Alessandro Volta, it is named after the Baltic German physicist Thomas Johann Seebeck, who in 1821 independently rediscovered it. It was observed that a compass needle would be deflected by a closed loop formed by two different
Thermoelectric effect
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generated at the junction per unit time is where formula_10 and formula_11 are the Peltier coefficients of conductors A and B, and formula_12 is the electric current (from A to B). The total heat generated is not determined by the Peltier effect alone, as it may also be influenced by Joule heating and thermal-gradient effects (see below). The Peltier coefficients represent how much heat is carried per unit charge. Since charge current must be continuous across a junction, the associated heat flow will develop a discontinuity if formula_10 and formula_11 are different. The Peltier effect can be considered as the
Thermoelectric effect
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to be controlled, but uses the heating time of a very small electric heating element as an analog. A rotary knob/cam arrangement is usually employed to switch-on the electric current to the "burner" and to also set the desired heating level. Within the device, the very small electric heating element heats a bimetallic strip. After some time, the bimetallic strip bends to open a set of switch contacts, thus interrupting the electric current to the heating element. At the same time, another (more robust) set of spring-loaded switch contacts, mounted in parallel with the former, also open, cutting off the
Infinite switch
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Staebler–Wronski effect The Staebler–Wronski Effect (SWE) refers to light-induced metastable changes in the properties of hydrogenated amorphous silicon. The defect density of hydrogenated amorphous silicon (a-Si:H) increases with light exposure, causing an increase in the recombination current and reducing the efficiency of the conversion of sunlight into electricity. It was discovered by David L. Staebler and Christopher R. Wronski in 1977. They showed that the dark current and photoconductivity of hydrogenated amorphous silicon can be reduced significantly by prolonged illumination with intense light. However, on heating the samples to above 150 °C, they could reverse the effect. The exact nature
Staebler–Wronski effect
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material from which the conductor is made, since its value depends on the type, number, and properties of the charge carriers that constitute the current. The Hall effect was discovered in 1879 by Edwin Hall while he was working on his doctoral degree at Johns Hopkins University in Baltimore, Maryland. Eighteen years before the electron was discovered, his measurements of the tiny effect produced in the apparatus he used were an experimental tour de force, published under the name "On a New Action of the Magnet on Electric Currents". The Hall effect is due to the nature of the current
Hall effect
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energy overall to achieve the same result. Design of an industrial heating system starts with assessment of the temperature required, the amount of heat required, and the feasible modes of transferring heat energy. In addition to conduction, convection and radiation, electrical heating methods can use electric and magnetic fields to heat material. Methods of electric heating include resistance heating, electric arc heating, induction heating, and dielectric heating. In some processes (for example, arc welding), electric current is directly applied to the workpiece. In other processes, heat is produced within the workpiece by induction or dielectric losses. As well, heat can
Electric heating
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of measuring electric current. The earliest galvanometer was reported by Johann Schweigger at the University of Halle on 16 September 1820. André-Marie Ampère also contributed to its development. Early designs increased the effect of the magnetic field generated by the current by using multiple turns of wire. The instruments were at first called "multipliers" due to this common design feature. The term "galvanometer," in common use by 1836, was derived from the surname of Italian electricity researcher Luigi Galvani, who in 1791 discovered that electric current would make a dead frog's leg jerk. Originally, the instruments relied on the Earth's
Galvanometer
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voltage. A radial current through a circular disc, subjected to a magnetic field perpendicular to the plane of the disc, produces a "circular" current through the disc. The absence of the free transverse boundaries renders the interpretation of the Corbino effect simpler than that of the Hall effect. Hall effect The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was discovered by Edwin Hall in 1879. For clarity, the original effect is sometimes
Hall effect
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similar to resistance welding, except that in the case of resistance welding the current is delivered using contacts to the workpiece instead of using induction. Induction welding Induction welding is a form of welding that uses electromagnetic induction to heat the workpiece. The welding apparatus contains an induction coil that is energised with a radio-frequency electric current. This generates a high-frequency electromagnetic field that acts on either an electrically conductive or a ferromagnetic workpiece. In an electrically conductive workpiece, the main heating effect is resistive heating, which is due to induced currents called eddy currents. In a ferromagnetic workpiece, the
Induction welding
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may precipitate out of solution and form a hard scale on the heating element surface, or may fall to the bottom of the tank and clog water flow. Maintenance of water heating equipment may require periodic removal of accumulated scale and sediment. Where water supplies are known to be highly mineralized, scale production can be reduced by using low-watt-density heating elements. Circulation heaters or "direct electric heat exchangers" (DEHE) use heating elements inserted into a "shell side" medium directly to provide the heating effect. All of the electric heat generated by the electric circulation heater is transferred into the medium,
Electric heating
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held in contact with the unknown sample that is locally heated to the probe temperature. It is used commercially to identify metal alloys. Thermocouples in series form a thermopile. Thermoelectric generators are used for creating power from heat differentials. The Peltier effect is the presence of heating or cooling at an electrified junction of two different conductors and is named after French physicist Jean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors, A and B, heat may be generated or removed at the junction. The Peltier heat
Thermoelectric effect
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Induction welding Induction welding is a form of welding that uses electromagnetic induction to heat the workpiece. The welding apparatus contains an induction coil that is energised with a radio-frequency electric current. This generates a high-frequency electromagnetic field that acts on either an electrically conductive or a ferromagnetic workpiece. In an electrically conductive workpiece, the main heating effect is resistive heating, which is due to induced currents called eddy currents. In a ferromagnetic workpiece, the heating is caused mainly by hysteresis, as the electromagnetic field repeatedly distorts the magnetic domains of the ferromagnetic material. In practice, most materials undergo a
Induction welding
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by the sintering community. Using a DC pulse as the electric current, spark plasma, spark impact pressure, joule heating, and an electrical field diffusion effect would be created. By modifying the graphite die design and its assembly, it was demonstrated to create Pressureless sintering condition in spark plasma sintering facility. This modified die design setup is reported to synergize the advantages of both conventional pressureless sintering and spark plasma sintering techniques. Electro sinter forging is an electric current assisted sintering (ECAS) technology originated from capacitor discharge sintering. It is used for the production of diamond metal matrix composites and under
Sintering
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This effect can require special consideration in the design of an electric system to serve non-linear loads. In addition to the increased line current, different pieces of electrical equipment can suffer effects from harmonics on the power system. Electric motors experience losses due to hysteresis and eddy currents set up in the iron core of the motor. These are proportional to the frequency of the current. Since the harmonics are at higher frequencies, they produce higher core losses in a motor than the power frequency would. This results in increased heating of the motor core, which (if excessive) can shorten
Harmonics (electrical power)
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perpendicular to the applied current. Due to the accumulation of electrons on one side of the sample, the number of collisions increases and a heating of the material occurs. This effect is quantified by the Ettingshausen coefficient "P", which is defined as: where "dT/dx" is the temperature gradient that results from the "y"-component "J" of an electric current density and the "z"-component "B" of a magnetic field. In most metals like copper, silver and gold "P" is on the order of and thus difficult to observe in common magnetic fields. In bismuth the Ettingshausen coefficient is several orders of magnitude
Ettingshausen effect
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has 15 million degree celsius temperature) which is required to initiate the fusion between hydrogen atoms, according to the latest test conducted in EAST ( test conducted in November 2018). Since the plasma is an electrical conductor, it is possible to heat the plasma by inducing a current through it; the induced current that provides most of the poloidal field is also a major source of initial heating. The heating caused by the induced current is called ohmic (or resistive) heating; it is the same kind of heating that occurs in an electric light bulb or in an electric heater.
Tokamak
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and the magnitude and distribution of residual compressive stress in the surface layer. The basis of all induction heating systems was discovered in 1831 by Michael Faraday. Faraday proved that by winding two coils of wire around a common magnetic core it was possible to create a momentary electromotive force in the second winding by switching the electric current in the first winding on and off. He further observed that if the current was kept constant, no EMF was induced in the second winding and that this current flowed in opposite directions subject to whether the current was increasing or
Induction hardening
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energy instead of drawing electric current off two plates attached to the crystal-faces. In 1821, Thomas Johann Seebeck discovered that a thermal gradient formed between two dissimilar conductors produces a voltage. At the heart of the thermoelectric effect is the fact that a temperature gradient in a conducting material results in heat flow; this results in the diffusion of charge carriers. The flow of charge carriers between the hot and cold regions in turn creates a voltage difference. In 1834, Jean Charles Athanase Peltier discovered that running an electric current through the junction of two dissimilar conductors could, depending on
Energy harvesting
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Ohm stated his law of electrical resistance in 1826, expressing the relationship between voltage, current, and resistance in an electric circuit. A year later, botanist Robert Brown discovered Brownian motion: pollen grains in water undergoing movement resulting from their bombardment by the fast-moving atoms or molecules in the liquid. In 1829, Gaspard Coriolis introduced the terms of work (force times distance) and kinetic energy with the meanings they have today. In 1831, Faraday (and independently Joseph Henry) discovered the reverse effect, the production of an electric potential or current through magnetism – known as electromagnetic induction; these two discoveries are
History of physics
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Zener effect In electronics, the Zener effect (employed most notably in the appropriately named Zener diode) is a type of electrical breakdown, discovered by Clarence Melvin Zener. It occurs in a reverse biased p-n diode when the electric field enables tunneling of electrons from the valence to the conduction band of a semiconductor, leading to a large number of free minority carriers which suddenly increase the reverse current. Under a high reverse-bias voltage the p-n junction's depletion region widens, leading to a high-strength electric field across the junction. Sufficiently strong electric fields enable tunneling of electrons across the depletion region
Zener effect
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radiation. This microwave auditory effect was thought to be caused by the microwaves inducing an electric current in the hearing centers of the brain. Research by NASA in the 1970s has shown this to be caused by thermal expansion in parts of the inner ear. In 1955 Dr. James Lovelock was able to reanimate rats frozen at 0 °C using microwave diathermy. When injury from exposure to microwaves occurs, it usually results from dielectric heating induced in the body. Exposure to microwave radiation can produce cataracts by this mechanism, because the microwave heating denatures proteins in the crystalline lens of
Microwave
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PEVA, EVA and some ABS plastics. Exercise caution when welding urethane as it has been known to give off cyanide gasses when melting. When an electrical insulator, like a plastic, is embedded with a material having high electrical conductivity, like metals or carbon fibers, induction welding can be performed. The welding apparatus contains an induction coil that is energised with a radio-frequency electric current. This generates an electromagnetic field that acts on either an electrically conductive or a ferromagnetic workpiece. In an electrically conductive workpiece, the main heating effect is resistive heating, which is due to induced currents called eddy
Plastic welding
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which an electric current is made to pass round the circuit. This reversible effect is proportional directly to the strength of the current, not to its square, as is the irreversible generation of heat due to resistance in all parts of the circuit. It is found that, if a current pass from an external source through a circuit of two metals, it cools one junction and heats the other. It cools the junction if it be in the same direction as the thermoelectric current which would be caused by directly heating that junction. In other words, the passage of a
Jean Charles Athanase Peltier
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efficiency in transferring heat. The thermal conductivity of heat pipes can be as high as 100,000 W/m K, in contrast to copper, which has a thermal conductivity of around 400 W/m K. Peltier cooling plates take advantage of the Peltier effect to create a heat flux between the junction of two different conductors of electricity by applying an electric current. This effect is commonly used for cooling electronic components and small instruments. In practice, many such junctions may be arranged in series to increase the effect to the amount of heating or cooling required. There are no moving parts, so
Thermal management (electronics)
118217
at right angles to it. 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. 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
Electricity
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less so, on fats and sugars. This is because fats and sugar molecules are far less polar than water molecules, and thus less affected by the forces generated by the alternating electromagnetic fields. Outside of cooking, the effect can be used generally to heat solids, liquids, or gases, provided they contain some electric dipoles. Dielectric heating involves the heating of electrically insulating materials by dielectric loss. A changing electric field across the material causes energy to be dissipated as the molecules attempt to line up with the continuously changing electric field. This changing electric field may be caused by an
Dielectric heating
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excess of electricity the plants can use cheap electricity to heat the hot water instead of finite bio or fossil fuels. As wind production rises the problem of too much electricity being generated will also give rise to new challenges and solutions. Electric heating and cooling can also be used in the form of more efficient heat pumps to mop up excess electricity supply. The electricity sector will in effect expand into the heating and cooling sector to displace current energy sources. RE thermal generation includes electricity generated from biofuels and electricity generated from the fraction of waste that is
Renewable energy in Denmark
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filament to the electrode, not the other way. So, alternating current (AC) signals can be converted into DC, or rectified. Hammer noted the rectifier effect when he added the third electrode to a heated filament light bulb. In September 1884, British scientist William Preece took back with him several of the Edison effect bulbs. He presented a paper on them in 1885, where he referred to thermionic emission as the "Edison Effect." The British physicist John Ambrose Fleming, who in 1882 had accepted a consulting position for the Edison & Swan Electric Light Company of London, discovered in 1885 that
William Joseph Hammer
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electromagnetic wave propagating in free space (as in a microwave oven), or it may be caused by a rapidly alternating electric field inside a capacitor. In the latter case, there is no freely-propagating electromagnetic wave, and the changing electric field may be seen as analogous to the electric component of an antenna near field. In this case, although the heating is accomplished by changing the electric field inside the capacitive cavity at radio-frequency (RF) frequencies, no actual radio waves are either generated or absorbed. In this sense, the effect is the direct electrical analog of magnetic induction heating, which is
Dielectric heating
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to a water supply and piping to transport product steam to the point of use. In places where electric power is relatively low cost compared to fossil fuels, it may be economically practical to use an electric boiler for steam central heating. For example, in Winnipeg, Canada, during the Second World War, large central electric steam boilers were used for a district heating system, using surplus hydroelectric power. The intent was to conserve coal fuel for more critical wartime needs. Electric boilers may rely on immersion heater resistance heating elements to heat water, or may use electric current passing directly
Electric boiler
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1831, Faraday (and independently Joseph Henry) discovered the reverse effect, the production of an electric potential or current through magnetism – known as electromagnetic induction; these two discoveries are the basis of the electric motor and the electric generator, respectively. In 1834, Carl Jacobi discovered his uniformly rotating self-gravitating ellipsoids (the Jacobi ellipsoid). In 1834, John Russell observed a nondecaying solitary water wave (soliton) in the Union Canal near Edinburgh and used a water tank to study the dependence of solitary water wave velocities on wave amplitude and water depth. In 1835, William Hamilton stated Hamilton's canonical equations of motion.
19th century in science
77117
Electric current An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionised gas (plasma). The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter. Electric currents cause Joule heating, which creates light in incandescent light bulbs. They
Electric current
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suppressing small-scale, localised instabilities. Calculations showed that this "stabilised pinch" would dramatically improve confinement times, and the older concepts "suddenly seemed obsolete". Marshall Rosenbluth, recently arrived at Los Alamos, began a detailed theoretical study of the pinch concept. With his wife Arianna and Richard Garwin, he developed "motor theory", or "M-theory", published in 1954. The theory predicted that the heating effect of the electric current was greatly increased with the power of the electric field. This suggested that the fast pinch concept would be more likely to succeed, as it was easier to produce larger currents in these devices. When
ZETA (fusion reactor)
869872
in regions that were outside the influence of the magnetic field. This counterflow limited the power output to the pickup wires, and induced waste heating of the copper disc. Later homopolar generators would solve this problem by using an array of magnets arranged around the disc perimeter to maintain a steady field effect in one current-flow direction. Another disadvantage was that the output voltage was very low, due to the single current path through the magnetic flux. Experimenters found that using multiple turns of wire in a coil could produce higher, more useful voltages. Since the output voltage is proportional
Electric generator
483898
component). For complicated waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is both unambiguous and has physical significance. For example, the "average" power transmitted by an acoustic or electromagnetic wave or by an electrical signal is proportional to the square of the RMS amplitude (and not, in general, to the square of the peak amplitude). For alternating current electric power, the universal practice is to specify RMS values of a sinusoidal waveform. One property of root mean square voltages and currents is that they produce the same heating effect as direct current in a
Amplitude
20780922
applied, the polymer will act as a heating resistor because of its resistivity. It will heat up homogeneously by the Joule effect until it reaches its melting temperature, beyond which it becomes sufficiently viscous to be malleable to the hand. Ideally the thermoplastic polymer selected has a relatively low melting temperature (60 ° C for example) so that the user can handle it without danger of burning and to reduce the amount of energy required for the transition. Any voltage can be used, both direct current and alternating current. However, the electric power required to do the rigid-malleable transition is
Electroformable material
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transport substances that solidify at ambient temperatures. Electric trace heating cables are an alternative to steam trace heating where steam is not available or unwanted. Electric trace heating began in the 1930s but initially no dedicated equipment was available. Mineral insulated cables ran at high current densities to produce heat, and control equipment was adapted from other applications. Mineral-insulated resistance heating cable was introduced in the 1950s, and parallel-type heating cables that could be cut to length in the field became available. Self-limiting thermoplastic cables were marketed in 1971. Control systems for trace heating systems developed from capillary filled-bulb thermostats
Trace heating
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current passing through the junction of two different metals. This is now called the Peltier effect (or Peltier–Seebeck effect). By switching the direction of current, either heating or cooling may be achieved. Junctions always come in pairs, as the two different metals are joined at two points. Thus heat will be moved from one junction to the other. The "Peltier effect" is the presence of heating or cooling at an electrified junction of two different conductors (1834). His great experimental discovery was the heating or cooling of the junctions in a heterogeneous circuit of metals according to the direction in
Jean Charles Athanase Peltier
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1883 Hopkinson showed mathematically that it was possible to connect two alternating current dynamos in parallel-—a problem that had long bedevilled electrical engineers. He also studied magnetic permeability at high temperature, and discovered what was later called the Hopkinson peak effect. The series-parallel method of electric motor control, for which Hopkinson was granted a British patent in 1881, would prove to be an important advance in the development of electric railways. He applied for a US patent in 1892, triggering an interference proceeding against American inventor Rudolph M Hunter, who had been granted a US patent for the method in
John Hopkinson
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has high harmonic content and relatively low power factor. This creates extra load on utility lines, increases heating of building wiring, the utility transformers, and standard AC electric motors, and may cause stability problems in some applications such as in emergency generator systems or aircraft generators. Harmonics can be removed by filtering, but the filters are expensive. Unlike displacement power factor created by linear inductive or capacitive loads, this distortion cannot be corrected by addition of a single linear component. Additional circuits are required to counteract the effect of the brief current pulses. Putting a current regulated boost chopper stage
Switched-mode power supply
8151097
Electric match An electric match is a device that uses an externally applied electric current to ignite a combustible compound. Electric matches use a bridgewire consisting of a heating element to ignite a pyrogen, which is a quantity of readily ignited pyrotechnic initiator composition. Electric matches can be used in any application where source of heat is needed at a precisely controlled point in time, typically to ignite a propellant or explosive. Examples include airbags, pyrotechnics, and military or commercial explosives. Electric matches consist of two parts, a bridgewire and a pyrogen. The bridgewire is a heating element, typically in
Electric match
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phenomenon discovered by Edwin Hall in 1879. Hall Effect current sensors can measure all types of current signals (i.e. AC, DC, or pulsating current). These sensors are currently being used widely in many industries because of their vast applications and the type of output they provide, which can be manipulated and can be used for various application. Current sensor A current sensor is a device that detects electric current in a wire, and generates a signal proportional to that current. The generated signal could be analog voltage or current or even a digital output. The generated signal can be then
Current sensor
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of photoeffect. Using this setup, he discovered the direct proportionality between the intensity of light and the induced photo electric current (the first law of photoeffect or Stoletov's law). One of his other findings resulted from measurements of the dependence of the intensity of the electric photo current on the gas pressure, where he found the existence of an optimal gas pressure P corresponding to a maximum photocurrent; this property was used for a creation of solar cells. In 1899, J. J. Thomson investigated ultraviolet light in Crookes tubes. Thomson deduced that the ejected particles were the same as those
Photoelectric effect
8268709
In the first half of the 19th century many very important additions were made to the world's knowledge concerning electricity and magnetism. For example, in 1819 Hans Christian Ørsted of Copenhagen discovered the deflecting effect of an electric current traversing a wire upon- a suspended magnetic needle. This discovery gave a clue to the subsequently proved intimate relationship between electricity and magnetism which was promptly followed up by Ampère who shortly thereafter (1821) announced his celebrated theory of electrodynamics, relating to the force that one current exerts upon another, by its electro-magnetic effects, namely Ampere brought a multitude of phenomena
History of electromagnetic theory
18615034
Thermoelectric battery A thermoelectric battery stores energy when charged by converting heat into chemical energy and produces electricity when discharged. Such systems potentially offer an alternative means of disposing of waste heat from plants that burn fossil fuels and/or nuclear energy. Thomas Johann Seebeck (1780-1831) discovered the thermoelectric effect in 1821. The symmetrical Peltier Effect (Jean Charles Athanse Peltier, 1785-1845) uses an electric current to produce temperature differences. In the middle part of the twentieth century the thermo-electric generator was often used in place of galvanic batteries. In 2014 researchers demonstrated a prototype system that uses copper electrodes and ammonia
Thermoelectric battery
77142
certain materials when cooled below a characteristic critical temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of "perfect conductivity" in classical physics. In a semiconductor it is sometimes useful to think of the current as due to the flow
Electric current
3643804
Hall effect was discovered by Hall in 1879, while working on his doctoral thesis in Physics. Hall's experiments consisted of exposing thin gold leaf (and, later, using various other materials) on a glass plate and tapping off the gold leaf at points down its length. The effect is a potential difference (Hall voltage) on opposite sides of a thin sheet of conducting or semiconducting material (the Hall element) through which an electric current is flowing. This was created by a magnetic field applied perpendicular to the Hall element. The ratio of the voltage created to the amount of current is
Edwin Hall
6742171
of the room, and change the output of the heater accordingly. Water can also be used as a heat-storage medium. An electric underfloor heating system has heating cables embedded in the floor. Current flows through a conductive heating material, supplied either directly from the line voltage (120 or 240 volts) or at low voltage from a transformer. The heated cables warm the flooring by direct conduction and will switch off once it reaches the temperature set by the floor thermostat. A warmer floor surface radiates heat to colder surrounding surfaces (ceiling, walls, furniture.) which absorb heat and reflects all non
Electric heating
66231
William Shockley developed the first semiconductor-based transistor, heralding a revolution in electronics. In 1879, Edwin Herbert Hall working at the Johns Hopkins University discovered a voltage developing across conductors transverse to an electric current in the conductor and magnetic field perpendicular to the current. This phenomenon arising due to the nature of charge carriers in the conductor came to be termed the Hall effect, but it was not properly explained at the time, since the electron was experimentally discovered 18 years later. After the advent of quantum mechanics, Lev Landau in 1930 developed the theory of Landau quantization and laid
Condensed matter physics
894759
deflexion on a magnetic needle (compass) when exposed to a temperature gradient. Because Ørsted had discovered that an electric current produces a deflexion on a compass transversal to the wire, Seebeck's results were interpreted as a thermoelectric effect. This is now called the Peltier–Seebeck effect and is the basis of thermocouples and thermopiles. In 1822, after previous experiments on voltaic current and magnetism, Thomas Johann Seebeck found that a circuit made from two dissimilar metals with junctions at different temperatures would deflect a compass magnet. Seebeck believed this was due to magnetism induced by the temperature difference. Based on this
Thomas Johann Seebeck
3029173
the Stark effect is either linear (proportional to the applied electric field) or quadratic with a high accuracy. The Stark effect can be observed both for emission and absorption lines. The latter is sometimes called the inverse Stark effect, but this term is no longer used in the modern literature. The effect is named after the German physicist Johannes Stark, who discovered it in 1913. It was independently discovered in the same year by the Italian physicist Antonino Lo Surdo, and in Italy it is thus sometimes called the Stark–Lo Surdo effect. The discovery of this effect contributed importantly to
Stark effect
426644
The heat generated depends on the resistance of the plasma and the amount of electric current running through it. But as the temperature of heated plasma rises, the resistance decreases and ohmic heating becomes less effective. It appears that the maximum plasma temperature attainable by ohmic heating in a tokamak is 20-30 million degrees Celsius. To obtain still higher temperatures, additional heating methods must be used. The current is induced by continually increasing the current through an electromagnetic winding linked with the plasma torus: the plasma can be viewed as the secondary winding of a transformer. This is inherently a
Tokamak
8151099
passed through the bridgewire, the resistive heating causes the element to rise above the ignition temperature of the pyrogen, and the pyrogen begins to burn. Commercial electric match manufacturers often specify 3 key parameters of an electric match: the resistance (often around 2 Ohm), a recommended firing current (often around 1 A), and a maximum no-fire current. The "test" button on a firing systems typically tests a setup by sending a current limited to well below the no-fire current (often 0.2 A) to detect common problems (short circuits and disconnected open circuits). A partial list of applications is: Electric matches,
Electric match
12515700
current. A portion of the solid electrolyte may also be resistively heated. The described or comparable cells may be incorporated into an oxygen detector or similar apparatus where the apparatus is operated by alternately heating the cell and measuring the emf developed by the cell across its electrode.The invention is also, in part, a unique, solid electrolyte-integral cell electrode/heater configuration which provides a zone of uniform maximum heating at a predetermined location within the electrolyte and which, when used with a suitable resistive heating electric current, confines the current to the integral electrode/heater prolonging cell life. Another aspect of the
William T. Kane
7517736
powders to close to their maximum theoretical densities. Electric current assisted sintering, also known as spark plasma sintering (SPS) relies on fast application of resistive heating and pressure to consolidate powders close to their maximum theoretical densities, without the undesired grain growth effect, thereby retaining close to original grain size and achieving improved mechanical properties in the final product. Work is progressing on bypassing the conventional route of atomising wrought feedstock or sponge and the inherent cost associated with the traditional Kroll process. Several of these processes, such as the FFC, MER Corporation, OS, Ginatta and BHP Billiton processes rely
Titanium powder
685757
some plastics absorb microwaves to the point that they may become dangerously hot. Products that are heated for too long can catch fire. Though this is inherent to any form of cooking, the rapid cooking and unattended nature of the use of microwave ovens results in additional hazard. Any metal or conductive object placed into the microwave will act as an antenna to some degree, resulting in an electric current. This causes the object to act as a heating element. This effect varies with the object's shape and composition, and is sometimes utilized for cooking. Any object containing pointed metal
Microwave oven
7821064
approach is by using a thermoelectric, such as those offered by Alphabet Energy, where a change in temperature across a semiconductor material creates a voltage through a phenomenon known as the Seebeck effect. A related approach is the use of thermogalvanic cells, where a temperature difference gives rise to an electric current in an electrochemical cell. Anthropogenic heat is heat generated by humans and human activity. The American Meteorological Society defines it as "Heat released to the atmosphere as a result of human activities, often involving combustion of fuels. Sources include industrial plants, space heating and cooling, human metabolism, and
Waste heat
580222
Yarkovsky effect The Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to meteoroids or small asteroids (about 10 cm to 10 km in diameter), as its influence is most significant for these bodies. The effect was discovered by the Polish civil engineer Ivan Osipovich Yarkovsky (1844–1902), who worked on scientific problems in his spare time. Writing in a pamphlet around the year 1900, Yarkovsky noted that the daily heating of a rotating object in space would cause it to
Yarkovsky effect
13552690
30 years to prevent condensation and provide radiant heat. Condensation in buildings can have serious consequences to health and property values. Heated or radiant glass is generally an enhanced standard two pane insulated glass window using various bus bar technologies to convey the electric current to heat the glass. Some technologies are patented and permit larger glass areas to be heated than others. In One university study shows that this heated glass technology is more efficient than other electric heating and can be more efficient than natural gas heating. Some environmentalists dispute the idea that this is an efficient heating
Heated glass
6491577
Pearson–Anson effect The Pearson–Anson effect, discovered in 1922 by Stephen Oswald Pearson and Horatio Saint George Anson, is the phenomenon of an oscillating electric voltage produced by a neon bulb connected across a capacitor, when a direct current is applied through a resistor. This circuit, now called the Pearson-Anson oscillator, neon lamp oscillator, or sawtooth oscillator, is one of the simplest types of relaxation oscillator. It generates a sawtooth output waveform. It has been used in low frequency applications such as blinking warning lights, stroboscopes, tone generators in electronic organs and other electronic music circuits, and in time bases and
Pearson–Anson effect
318987
cycler. The thermal cycler heats and cools the reaction tubes to achieve the temperatures required at each step of the reaction (see below). Many modern thermal cyclers make use of the Peltier effect, which permits both heating and cooling of the block holding the PCR tubes simply by reversing the electric current. Thin-walled reaction tubes permit favorable thermal conductivity to allow for rapid thermal equilibration. Most thermal cyclers have heated lids to prevent condensation at the top of the reaction tube. Older thermal cyclers lacking a heated lid require a layer of oil on top of the reaction mixture or
Polymerase chain reaction
7882188
rods increased significantly when exposed to strong light. Smith described the "Effect of Light on Selenium during the passage of an Electric Current" in an article that was published in the 20 February 1873 issue of Nature. Willoughby Smith Willoughby Smith (6 April 1828, Great Yarmouth, Norfolk – 17 July 1891, Eastbourne, Sussex) was an English electrical engineer who discovered the photoconductivity of the element selenium. This discovery led to the invention of photoelectric cells, including those used in the earliest television systems. In 1848, he began working for the Gutta Percha Company, London where he developed iron and copper
Willoughby Smith
5186499
ammonia, alcohols, and with heating. ICN slowly reacts with water or carbon dioxide to produce hydrogen cyanide. It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. Cyanogen iodide solutions in pyridine conduct electric current. Dilute solutions of ICN in pyridine are colorless at first, but upon standing become successively yellow, orange, red-brown and deep red-brown. This effect is due to a change
Cyanogen iodide
3002286
can have a coefficient of more than 1.0 since it moves additional thermal energy from the environment to the heated item. The definition of the efficiency of a heating process requires defining the boundaries of the system to be considered. When heating a building, the overall efficiency is different when considering heating effect per unit of electric energy delivered on the customer's side of the meter, compared to the overall efficiency when also considering the losses in the power plant and transmission of power. In the energy balance of groundwater flow a hydraulic equivalent of Joule's law is used: where:
Joule heating
16089910
cooling, a side-effect which contributes to total energy consumption. However, when heating is needed, waste heat from plug loads also supplies part of the energy requirement for heating. Heating a space with electric heating is environmentally less effective than using the electricity for heat pumps, or using other sources of energy such as natural gas. In general, although total plug load energy use is increasing, the actual plug load equipment stock is getting more efficient; technical advances such as low power consumption by LCD monitors, more effective sleep modes and the uptake of the notebook laptop computer in lieu of
Plug load
5875691
to give a higher voltage, and consequently higher current, and make the trace heating elements a bit hotter. The boost system is usually on a timer and switches back to 'normal' after a period of time. Trace heating Electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe is usually covered with thermal insulation to retain heat losses from the pipe. Heat generated by the element
Trace heating
7445483
unit, located between the blanket and the electrical outlet, manages the amount of current entering into the heat elements in the blanket. Some modern electric blankets use carbon fiber elements that are far less bulky and conspicuous than older heating wires. Carbon fiber is also used as the heating element in many high-end heated car seats. Blankets can be purchased with rheostats that regulate the heat by managing body heat and blanket temperatures, ensuring a comfortable experience. Newer electric blankets have a shutoff mechanism to prevent the blanket from overheating or catching fire. Older blankets (prior to about 2001) may
Electric blanket
12578710
development of ERH - to enhance oil recovery (see above). Electrical resistance heating remediation Electrical Resistance Heating (ERH) is an intensive in situ environmental remediation method that uses the flow of alternating current electricity to heat soil and groundwater and evaporate contaminants. Electric current is passed through a targeted soil volume between subsurface electrode elements. The resistance to electrical flow that exists in the soil causes the formation of heat; resulting in an increase in temperature until the boiling point of water at depth is reached. After reaching this temperature, further energy input causes a phase change, forming steam and
Electrical resistance heating remediation
1753171
Single-phase electric power In electrical engineering, single-phase electric power is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads are mostly lighting and heating, with few large electric motors. A single-phase supply connected to an alternating current electric motor does not produce a revolving magnetic field; single-phase motors need additional circuits for starting (capacitor start motor), and such motors are uncommon above 10 kW in rating. Because the voltage of a single phase system reaches a peak value twice in each cycle,
Single-phase electric power
20739874
is needed to produce electrical current. Electrodes, in direct contact with food, pass electric current through the matrix. The distance between the electrodes can be adjusted to achieve the optimum electrical field strength. The generator creates the electrical current which flows to the first electrode and passes through the food product placed in the electrode gap. The food product resists the flow of current causing internal heating. The current continues to flow to the second electrode and back to the power source to close the circuit. The insulator caps around the electrodes controls the environment within the system. The electrical
Ohmic heating (food processing)
7189306
encouraging the use of electricity for space heating and water heating. This can be regarded as an economically wasteful practice. However, as the adoption of electric cars, such as the French Renault Fluence Z.E., over internal combustion engine vehicles increases, reducing fossil fuel dependence, France's comparatively cheap peak and off peak electricity prices could act as a strong customer incentive that may spur the speed of the adoption of electric vehicles, essentially turning the current perceived glut of relatively cheap fission-electricity into an asset, as demand for electric vehicle recharging stations becomes more and more commonplace. Due to France's very
Nuclear power in France
521164
load impedance equal to Z, in which case the transmission line is said to be "matched". Some of the power that is fed into a transmission line is lost because of its resistance. This effect is called "ohmic" or "resistive" loss (see ohmic heating). At high frequencies, another effect called "dielectric loss" becomes significant, adding to the losses caused by resistance. Dielectric loss is caused when the insulating material inside the transmission line absorbs energy from the alternating electric field and converts it to heat (see dielectric heating). The transmission line is modelled with a resistance (R) and inductance (L)
Transmission line
8268713
the junction of the metals, depending on the direction of the current. This is termed the Peltier effect. The variations of temperature are found to be proportional to the strength of the current and not to the square of the strength of the current as in the case of heat due to the ordinary resistance of a conductor. This second law is the IR law, discovered experimentally in 1841 by the English physicist Joule. In other words, this important law is that the heat generated in any part of an electric circuit is directly proportional to the product of the
History of electromagnetic theory
5153305
also near-field effect (thus not involving radio waves). Frequencies in the range of 10–100 MHz are necessary to cause dielectric heating, although higher frequencies work equally well or better, and in some materials (especially liquids) lower frequencies also have significant heating effects, often due to more unusual mechanisms. For example, in conductive liquids such as salt water, "ion-drag" causes heating, as charged ions are "dragged" more slowly back and forth in the liquid under influence of the electric field, striking liquid molecules in the process and transferring kinetic energy to them, which is eventually translated into molecular vibrations and thus
Dielectric heating
869870
electrically charged belts, plates, and disks that carried charge to a high potential electrode. The charge was generated using either of two mechanisms: electrostatic induction or the triboelectric effect. Such generators generated very high voltage and low current. Because of their inefficiency and the difficulty of insulating machines that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. Their only practical applications were to power early X-ray tubes, and later in some atomic particle accelerators. The operating principle of electromagnetic generators was discovered in the years
Electric generator
10392577
methods uses alternating currents (AC) to induce electric charges in the subsurface, and the apparent resistivity is measured at different AC frequencies. Induced polarization Induced polarization (IP) is a geophysical imaging technique used to identify the electrical chargeability of subsurface materials, such as ore. The polarization effect was originally discovered by Conrad Schlumberger when measuring the resistivity of rock. The survey method is similar to electrical resistivity tomography (ERT), in that an electric current is transmitted into the subsurface through two electrodes, and voltage is monitored through two other electrodes. Induced polarization is a geophysical method used extensively in mineral
Induced polarization
3693147
electric kettles are commonly used to boil water without the necessity of a stove top. The heating element is typically fully enclosed, with a power rating of 2–3 kW. This means that the current draw for an electric kettle is upwards 10 A, which is a sizeable proportion of the current available for a typical home: the main fuse of most homes varies between 20 and 100 A. For this reason electric kettles, while available, are much less popular in countries with 110 V mains electricity. At half the voltage, the current would need to be double to attain the
Kettle
12578695
Electrical resistance heating remediation Electrical Resistance Heating (ERH) is an intensive in situ environmental remediation method that uses the flow of alternating current electricity to heat soil and groundwater and evaporate contaminants. Electric current is passed through a targeted soil volume between subsurface electrode elements. The resistance to electrical flow that exists in the soil causes the formation of heat; resulting in an increase in temperature until the boiling point of water at depth is reached. After reaching this temperature, further energy input causes a phase change, forming steam and removing volatile contaminants. ERH is typically more cost effective when
Electrical resistance heating remediation
13127624
of heat. Joule Heating is a predominant mechanism for heat generation in integrated circuits and is an undesired effect in most of the cases. For an ohmic material, it has the form: Where formula_4 is the current density in <nowiki>[</nowiki>A·m<nowiki>]</nowiki>, formula_5 is the specific electric resistivity in <nowiki>[</nowiki>formula_6·m<nowiki>]</nowiki> and formula_7 is the generated heat per unit volume in <nowiki>[</nowiki>W·m<nowiki>]</nowiki>. The governing equation of the physics of the heat transfer problem relates the flux of heat in space, its variation in time and the generation of power by the following expression: Where formula_2 is the thermal conductivity, formula_10 is the density
Thermal simulations for integrated circuits
3052046
Induction heating Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, through heat generated in the object by eddy currents. An induction heater consists of an electromagnet, and an electronic oscillator that passes a high-frequency alternating current (AC) through the electromagnet. The rapidly alternating magnetic field penetrates the object, generating electric currents inside the conductor called eddy currents. The eddy currents flowing through the resistance of the material heat it by Joule heating. In ferromagnetic (and ferrimagnetic) materials like iron, heat may also be generated by magnetic hysteresis losses. The frequency of
Induction heating
9619070
used in space probes, which has the same mechanism but use radioisotopes to generate the required heat difference. In 1821, Thomas Johann Seebeck rediscovered that a thermal gradient formed between two dissimilar conductors can produce electricity. At the heart of the thermoelectric effect is the fact that a temperature gradient in a conducting material results in heat flow; this results in the diffusion of charge carriers. The flow of charge carriers between the hot and cold regions in turn creates a voltage difference. In 1834, Jean Charles Athanase Peltier discovered the reverse effect, that running an electric current through the
Thermoelectric generator
1902190
Skin effect Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor. The skin effect is due to opposing eddy currents
Skin effect
2580085
pumps exploit this phenomenon, as do thermoelectric cooling devices found in refrigerators. In different materials, the Seebeck coefficient is not constant in temperature, and so a spatial gradient in temperature can result in a gradient in the Seebeck coefficient. If a current is driven through this gradient, then a continuous version of the Peltier effect will occur. This Thomson effect was predicted and subsequently observed in 1851 by Lord Kelvin (William Thomson). It describes the heating or cooling of a current-carrying conductor with a temperature gradient. If a current density formula_16 is passed through a homogeneous conductor, the Thomson effect
Thermoelectric effect
43387
assumptions on the spectrum of particles or operators. In tokamak fusion devices, bootstrapping refers to the process in which a bootstrap current is self-generated by the plasma, which reduces or eliminates the need for an external current driver. Maximising the bootstrap current is a major goal of advanced tokamak designs. Bootstrapping in inertial confinement fusion refers to the alpha particles produced in the fusion reaction providing further heating to the plasma. This heating leads to ignition and an overall energy gain. Bootstrapping is a form of positive feedback in analog circuit design. An electric power grid is almost never brought
Bootstrapping