chemical analysis: Conductometry: …of the resistance is the conductance (G = 1/R). As the conductance of a solution increases, its ability to conduct an electric current increases.

electricity: Conductors, insulators, and semiconductors: In a conductor, the valence band is partially filled, and since there are numerous empty levels, the electrons are free to move under the influence of an electric field; thus, in a metal the valence band is also the conduction band. In an insulator, electrons completely fill…

high-pressure phenomena: Effects on electric and magnetic properties: Nevertheless, electric conductivities of numerous materials at high pressures have been documented. The principal classes of solids—insulators, semiconductors, metals, and superconductors—are distinguished on the basis of electric conductivity and its variation with temperature. Insulators, which include most rock-forming oxides and silicates, have been investigated extensively by…

electricity: Conductors, insulators, and semiconductors: …or semiconductors according to their electric conductivity. The classifications can be understood in atomic terms. Electrons in an atom can have only certain well-defined energies, and, depending on their energies, the electrons are said to occupy particular energy levels. In a typical atom with many electrons, the lower energy levels…

solar cell: Solar cell structure and operation: Two additional electrical contact layers are needed to carry the electric current out to an external load and back into the cell, thus completing an electric circuit. The electrical contact layer on the face of the cell where light enters is generally present in some grid pattern…

stagecraft: Flying systems: …this type is reliant on electrical counterweight-assisted hoists. There are, in turn, two forms of electrical counterweight-assisted hoists: traction drive and linkage drive. In the traction-drive system, the hoisting line–counterweight system is not directly coupled to the electric motor drive, and slippage may occur during acceleration and deceleration of the…

defibrillation, the administration of electric shocks to the heart in order to reset normal heart rhythm in persons who are experiencing cardiac arrest or whose heart function is endangered because of severe arrhythmia (abnormality of heart rhythm). There are several different kinds of

differentiator: There are also electronic differentiators, or electrical differentiating circuits. The Figure shows a differentiator based on an electrical analog. For a time-varying input, if the capacitive reactance XC shown in the schematic diagram is very large compared with the resistance R, the current, and hence output voltage

stagecraft: Control consoles: The earliest electrical dimmer switchboard, or control console—a device that centralizes control of the intensity of the stage lights—resembled the gas table that was used with gas lights in the late 19th century. These first electrical switchboards, introduced in Europe and the United…

animal communication: …sound, colour pattern, posture, movement, electrical discharge, touch, release of an odorant, or some combination of these mediums.

electrical double layer, region of molecular dimension at the boundary of two substances across which an electrical field exists. The substances must each contain electrically charged particles, such as electrons, ions, or molecules with a separation of electrical charges (polar molecules). In the

electrical and electronics engineering, the branch of engineering concerned with the practical applications of electricity in all its forms, including those of the field of electronics. Electronics engineering is that branch of electrical engineering concerned with the uses of the electromagnetic

explosive: Electrical firing: The principal advantages of electric over fuse firing are exact control of the time when the blast is initiated, the simultaneous firing of a number of shots, if that is desired, and the ability to obtain a very high degree of water resistance.…

hygrometer: Electrical hygrometers measure the change in electrical resistance of a thin layer of lithium chloride, or of a semiconductor device, as the humidity changes. Other hygrometers sense changes in weight, volume, or transparency of various substances that react to humidity.

electrical impedance, measure of the total opposition that a circuit or a part of a circuit presents to electric current. Impedance includes both resistance and reactance. The resistance component arises from collisions of the current-carrying charged particles with the internal structure of the

chromatography: Chromatography–mass spectrometry methods: Modern electronic integrators will, when properly instructed, ignore electronic noise, compensate for baseline drift, start integration when a peak appears, integrate, and stop the process when the peak exits the detector. Integration, a process of summation, is accomplished by opening and closing a narrow electronic window,…

Benedict Cumberbatch: Doctor Strange and The Grinch: …camp for 14 years, and The Electrical Life of Louis Wain, a biopic about a British artist who was known for his anthropomorphic drawings of cats. However, his most notable performance that year was in Jane Campion’s The Power of the Dog, a western about a rancher whose cruelty—especially toward…

Oliver Heaviside: In Electrical Papers (1892), he dealt with theoretical aspects of problems in telegraphy and electrical transmission, making use of an unusual calculatory method called operational calculus, now better known as the method of Laplace transforms, to study transient currents in networks. His work on the theory…

history of film: Introduction of sound: …Electric’s newly created marketing subsidiary, Electrical Research Products, Incorporated (ERPI), to use Western Electric equipment with the Movietone sound-on-film recording system. ERPI’s monopoly did not please the Radio Corporation of America (RCA), which had tried to market a sound-on-film system that had been developed in the laboratories of its parent…

resistance, in electricity, property of an electric circuit or part of a circuit that transforms electric energy into heat energy in opposing electric current. Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors.

electrical shock, the perceptible and physical effect of an electrical current that enters the body. The shock may range from an unpleasant but harmless jolt of static electricity, received after one has walked over a thick carpet on a dry day, to a lethal discharge from a power line. The great

steel: Electrical steels: An important group of steels, necessary for the generation and transmission of electrical power, is the high-silicon electrical steels. Electromagnets for alternating current are always made by laminating many thin sheets, which are insulated in order to minimize the flow of eddy currents…

pain: Alleviation of pain: …pain may be treated by transcutaneous electrical nerve stimulation (TENS), in which electrodes are placed on the skin above the painful area. The stimulation of additional peripheral nerve endings has an inhibitory effect on the nerve fibres generating the pain. Acupuncture, compresses, and heat treatment may operate by the same…

meat processing: Stunning: …methods of stunning are mechanical, electrical, and carbon dioxide (CO2) gas. The end result of each method is to render the animal unconscious. Mechanical stunning involves firing a bolt through the skull of the animal using a pneumatic device or pistol. Electrical stunning passes a current of electricity through the…

South Africa: Resources and power: …electric power is generated by ESKOM at huge stations in Mpumalanga. Synthetic fuel derived from coal supplies a small proportion of the country’s energy needs, as does imported oil refined at the ports or piped to a major inland refinery at Sasolburg. A nuclear power plant at Duinefonte has operated…

automobile: Electrical system: The electrical system comprises a storage battery, generator, starting (cranking) motor, lighting system, ignition system, and various accessories and controls. Originally, the electrical system of the automobile was limited to the ignition equipment. With the advent of the electric starter on a 1912…

tachometer: Electrical tachometers are of several types. The eddy-current, or drag, type is widely used in automobile speedometers; a magnet rotated with the shaft being measured produces eddy currents that are proportional to angular speed. Electric-generator tachometers work by generating either an alternating or a direct…

aversion therapy: In the electrical therapy, the patient is given a lightly painful shock whenever the undesirable behaviour is displayed. This method has been used in the treatment of sexual deviations. In the chemical therapy, the patient is given a drug that produces unpleasant effects, such as nausea, when…

transducer: Electrical transducers may be classified as active or passive. The active transducers generate electric current or voltage directly in response to stimulation. An example is the thermocouple; here, the fact that a current will flow in a continuous circuit of two metals, if the two…

nervous system: Transmission at the synapse: In electrical transmission, the ionic current flows directly through channels that couple the cells. In chemical transmission, a chemical substance called the neurotransmitter passes from one cell to the other, stimulating the second cell to generate its own action potential.

Amalgamated Engineering and Electrical Union: …Engineering Union (AEU) with the Electrical, Electronic, Telecommunication and Plumbing Union (EETPU).

machine tool: Electrical-discharge machining (EDM): EDM involves the direction of high-frequency electrical spark discharges from a graphite or soft metal tool, which serves as an electrode, to disintegrate electrically conductive materials such as hardened steel or carbide. The electrode and workpiece are immersed in a dielectric liquid, and…

thermometer: Electrical-resistance thermometers characteristically use platinum and, like thermistors, operate on the principle that electrical resistance varies with changes in temperature. However, they can measure a much greater temperature range than thermistors. Thermocouples are among the most widely used industrial thermometers. They are composed of two…

computer memory: Semiconductor memory: EPROM (erasable programmable ROM), EAROM (electrically alterable ROM), and flash memory are types of nonvolatile memories that are rewritable, though the rewriting is far more time-consuming than reading. They are thus used as special-purpose memories where writing is seldom necessary—if used for the BIOS, for example, they may be…

electricity, phenomenon associated with stationary or moving electric charges. Electric charge is a fundamental property of matter and is borne by elementary particles. In electricity the particle involved is the electron, which carries a charge designated, by convention, as negative. Thus, the

solar cell: Solar panel design: …solar arrays with public utility power grids in two ways. One-way systems are used by utilities to supplement power grids during midday peak usage. Bidirectional systems are used by companies and individuals to supply some or all of their power needs, with any excess power fed back into a utility…

fence: Electrified fences, frequently a single strand of barbed wire, are sometimes used for temporary confinement of animals. A mild electric shock is given to the animal at intervals of a few seconds if it is in contact with the fence.

Musicland Studios: Machine-Made Music from Munich: …the development of the synthesizer, electro-disco was dreamed up at Musicland in the mid-1970s by producer Giorgio Moroder (an Italian synthesizer player), his partner Peter Bellotte (an Italian guitarist and lyricist), and Donna Summer (an American vocalist).

industrial glass: Flat glass: ) A further development, the electro-float process, introduced in 1967, made it possible to implant copper and other metal ions into the upper surface of glass using tin as an electrode at the bottom and a fixed copper (or other metal) electrode halfway down the bath at the top.

electricity: Electro-optic phenomena: The index of refraction n of a transparent substance is related to its electric polarizability and is given by n2 = 1 + χe/ε0. As discussed earlier, χe is the electric susceptibility of a medium, and the equation P = χeE relates the

optical ceramics: Electro-optical components: Electro-optical ceramics are materials that combine optical transparency with voltage-variable optical, or electro-optical (EO), behaviour. Single-crystal EO materials include lithium niobate (LiNbO3) and lithium tantalate (LiTaO3); polycrystalline EO materials include a lanthanum-modified lead zirconate tantalate known as PLZT. Among other EO properties, these materials exhibit…

electricity: Electro-optic phenomena: …and is known as the Pockels effect (after the German physicist F. R. Pockels).

Kerr electro-optic effect: The Kerr cell, also referred to as a Kerr electro-optical shutter, is a device employing the Kerr effect to interrupt a beam of light up to 1010 times per second. Linearly polarized light (light vibrating in one plane, as shown in the Figure) is passed through…

telecommunications media: Electro-optical transmitters: The efficiency of an electro-optical transmitter is determined by many factors, but the most important are the following: spectral line width, which is the width of the carrier spectrum and is zero for an ideal monochromatic light source; insertion loss, which is the…

electrophoresis: …fixed diaphragm—the phenomenon is called electroosmosis.

electromechanical transducer: any type of device that either converts an electrical signal into sound waves (as in a loudspeaker) or converts a sound wave into an electrical signal (as in the microphone). Many of the transducers used in everyday life operate in both directions, such as the…

electronic carillon, 20th-century musical instrument in which the acoustical tone source—metal tubes, rods, or bars struck by hammers—is picked up electromagnetically or electrostatically and converted into electrical vibrations that are highly amplified and fed into loudspeakers placed in a belfry

chemical analysis: Electroanalysis: The second major category of instrumental analysis is electroanalysis. The electroanalytical methods use electrically conductive probes, called electrodes, to make electrical contact with the analyte solution. The electrodes are used in conjunction with electric or electronic devices to which they are attached to measure…

mechanoreception: Slight deformation of any mechanoreceptive nerve cell ending results in electrical changes, called receptor or generator potentials, at the outer surface of the cell, and this in turn induces the appearance of impulses (“spikes”) in the associated nerve fibre. Various laboratory devices are used to record…

electrocardiography, method of graphic tracing (electrocardiogram; ECG or EKG) of the electric current generated by the heart muscle during a heartbeat. The tracing is recorded with an electrocardiograph (actually a relatively simple string galvanometer), and it provides information on the

electrocardiography, method of graphic tracing (electrocardiogram; ECG or EKG) of the electric current generated by the heart muscle during a heartbeat. The tracing is recorded with an electrocardiograph (actually a relatively simple string galvanometer), and it provides information on the

electrochemical reaction: Electrocatalysis: The problems related to the increase of rates of electrochemical reactions, or, to put it another way, the decrease of overpotential, needed to perform reactions at a given rate are the subject of electrocatalysis. Both increase and decrease are of considerable practical importance since…

surgery: Present-day surgery: …may also be controlled by electrocautery, the use of an instrument heated with an electric current to cauterize, or burn, vessel tissue. The most commonly used instruments in surgery are still the scalpel (knife), hemostatic forceps, flexible tissue-holding forceps, wound retractors for exposure, crushing and noncrushing clamps for intestinal and…

electroceramics, category of advanced ceramic materials that are employed in a wide variety of electric, optical, and magnetic applications. In contrast to traditional ceramic products such as brick and tile, which have been produced in various forms for thousands of years, electroceramics are a

chemical analysis: Electroanalysis: The second major category of instrumental analysis is electroanalysis. The electroanalytical methods use electrically conductive probes, called electrodes, to make electrical contact with the analyte solution. The electrodes are used in conjunction with electric or electronic devices to which they are attached to measure…

electrolytic cell, any device in which electrical energy is converted to chemical energy, or vice versa. Such a cell typically consists of two metallic or electronic conductors (electrodes) held apart from each other and in contact with an electrolyte (q.v.), usually a dissolved or fused ionic

materials testing: Corrosion: …contact between the two metals, corroding the aluminum.

Jöns Jacob Berzelius: Electrochemical dualism: Berzelius is best known for his system of electrochemical dualism. The electrical battery, invented in 1800 by Alessandro Volta and known as the voltaic pile, provided the first experimental source of current electricity. In 1803 Berzelius demonstrated, as did the English chemist Humphry…

machine tool: Electrochemical machining (ECM): ECM resembles electroplating in reverse. In this process metal is dissolved from a workpiece with direct current at a controlled rate in an electrolytic cell. The workpiece serves as the anode and is separated by a gap of 0.001 to 0.030 inch (0.025…

electrochemical reaction, any process either caused or accompanied by the passage of an electric current and involving in most cases the transfer of electrons between two substances—one a solid and the other a liquid. Under ordinary conditions, the occurrence of a chemical reaction is accompanied

chemical analysis: Luminescence: … causes the luminescence, it is electrochemiluminescence.

electrochemistry, branch of chemistry concerned with the relation between electricity and chemical change. Many spontaneously occurring chemical reactions liberate electrical energy, and some of these reactions are used in batteries and fuel cells to produce electric power. Conversely, electric

human ear: Audiometry: …type of test is the electrocochleogram (ECoG). Electric potentials representing impulses in the cochlear nerve are recorded from the outer surface of the cochlea by means of a fine, insulated needle electrode inserted through the tympanic membrane to make contact with the promontory of the basal turn. This test provides…

shock therapy, method of treating certain psychiatric disorders through the use of drugs or electric current to induce shock; the therapy derived from the notion (later disproved) that epileptic convulsions and schizophrenic symptoms never occurred together. In 1933 the psychiatrist Manfred Sakel

electrochemical reaction: Electrocrystallization: Deposition of metals and other substances at electrodes as a consequence of an electrode process exhibits a number of specific features. The electrode process is followed by crystal building, and this results in a continuous change of the electrode surface. This change, in turn,…

electrocution, method of execution in which the condemned person is subjected to a heavy charge of electric current. Once the most widely used method of execution in the United States, electrocution was largely supplanted by lethal injection in the late 20th and early 21st centuries and is now used

reaction mechanism: Electrocyclic: In a third class of additions, both portions of the attacking reagent combine simultaneously with the substrate. Reactions of this kind sometimes retain predominantly electrophilic or predominantly nucleophilic character, as can be shown by structural and environmental effects. In a number of important cases,…

bioelectricity: …a flattened cell called an electroplaque. Large numbers of electroplaques are arranged in series and in parallel to build up voltage and current-producing capacity of the electric organ. Fishes deliver a sudden discharge of electricity by timing the nervous impulses that activate individual electroplaques, thereby providing simultaneous action of the…

electrode, electric conductor, usually metal, used as either of the two terminals of an electrically conducting medium; it conducts current into and out of the medium, which may be an electrolytic solution as in a storage battery, or a solid, gas, or vacuum. The electrode from which electrons

spectroscopy: Line sources: …are hollow cathode lamps and electrodeless lamps driven by microwave radiation. If specific atomic lines are desired, a small amount of the desired element is introduced in the discharge.

integrated circuit: Chemical methods: …chemical methods of deposition are electrodeposition (or electroplating) and thermal oxidation. In the former the substrate is given an electrically conducting coating and placed in a liquid solution (electrolyte) containing metal ions, such as gold, copper, or nickel. A wide range of film thicknesses can be built. In thermal oxidation…

psychogalvanic reflex (PGR), a change in the electrical properties of the body (probably of the skin) following noxious stimulation, stimulation that produces emotional reaction, and, to some extent, stimulation that attracts the subject’s attention and leads to an aroused alertness. The response

separation and purification: Barrier separations: In electrodialysis, an electrical field accelerates the migration.

electrochemical reaction: History: …the transfer of electrons (called electrodics), gained in importance and became the main aspect of electrochemistry. From about 1960, electrodics began to develop as an interdisciplinary area in the search for solutions to problems such as the source of energy in space flights from fuel cells, the stability of metals…

machine tool: Electrical-discharge machining (EDM): EDM involves the direction of high-frequency electrical spark discharges from a graphite or soft metal tool, which serves as an electrode, to disintegrate electrically conductive materials such as hardened steel or carbide. The electrode and workpiece are immersed in a dielectric liquid, and…

ammeter: The electrodynamic ammeter uses a moving coil rotating in the field produced by a fixed coil. It measures direct and alternating current (by using a rectifier to convert the AC to DC) with accuracies of 0.1 to 0.25 percent. In the thermal (or hot-wire) ammeter, used…

maglev: Electromagnetic suspension (EMS) and electrodynamic suspension (EDS): Electrodynamic suspension (EDS) systems are similar to EMS in several respects, but the magnets are used to repel the train from the guideway rather than attract them. These magnets are supercooled and superconducting and have the ability to conduct electricity for a short time after…

transducer, device that converts input energy into output energy, the latter usually differing in kind but bearing a known relation to input. Originally, the term referred to a device that converted mechanical stimuli into electrical output, but it has been broadened to include devices that sense

electromagnetism: Foundations of electrochemistry and electrodynamics: The invention of the battery in 1800 made possible for the first time major advances in the theories of electric current and electrochemistry. Both science and technology developed rapidly as a direct result,

electroencephalography, technique for recording and interpreting the electrical activity of the brain. The nerve cells of the brain generate electrical impulses that fluctuate rhythmically in distinct patterns. In 1929 German scientist Hans Berger published the results of the first study to employ

electroencephalography, technique for recording and interpreting the electrical activity of the brain. The nerve cells of the brain generate electrical impulses that fluctuate rhythmically in distinct patterns. In 1929 German scientist Hans Berger published the results of the first study to employ

electrophotography: A proprietary process known as Electrofax employs a photographic paper coated with a dielectric layer; the entire charging, exposure, and development process is thus effected directly on the paper itself.

electroforming, making duplicates by electroplating metal onto a mold of an object, then removing the mold. Intricate surface details are exactly reproduced by this process, which is used to make masters for pressing phonograph records. Electroforming is also used for reproducing medals and for

colorectal cancer: Treatment: …them in a procedure called electrofulguration. In cases where the lower portion of the rectum is involved, a colostomy may be required, whereby the surgeon creates an artificial opening for the removal of waste. If colorectal cancer has spread to surrounding tissues such as those of the uterus, prostate, liver,…

steel: Surface coating: Electrolytic galvanizing lines have similar entry and exit sections, but they deposit zinc in as many as 20 consecutive electrolytic coating cells. Of the several successful cell designs, the simple vertical cell (B in the figure) is discussed here to explain the principle. The strip,…

electrogasdynamics, study of the forces produced by the motion of electrically charged particles (ions) carried by an insulating gas flowing through an electric field. See also magnetohydrodynamic power

chemical analysis: Electrogravimetry: This method employs an electric current to deposit a solid on an electrode from a solution. Normally the deposit is a metallic plate that has formed from the corresponding metallic ions in the solution; however, other electrode coatings also can be formed. The use…

virtual sit-in: …Disturbance Theater, the Electrohippies (now Electrohippies Collective), and RTMark—were known for their “hactivism.” In 1998 Electronic Disturbance Theater held one of the first virtual sit-ins. The action was in solidarity with the Zapatista National Liberation Army (EZLN), a Mexican guerrilla group, and was directed against the Mexican government. The Electrohippies,…

electrojet, streaming movement of charged particles in the lower ionosphere. The term is limited by some to those flow patterns that contain a significant proportion of neutral gases, but highly concentrated, laterally limited, electric currents are also called electrojets. The latter circulate

electroless plating, nonelectrical plating of metals and plastics to achieve uniform coatings by a process of controlled autocatalytic (self-continuing) reduction. Discovered in 1944 by A. Brenner and G.E. Riddell, electroless plating involves the deposition of such metals as copper, nickel,

electroluminescence, production of light by the flow of electrons, as within certain crystals. Electroluminescence is one of the few instances in which a direct conversion of electric energy into visible light takes place without the generation of heat, such as occurs in the incandescent lamp.

lamp: Modern electrical light sources: The electroluminescent lamp, another semiconductor lamp, consists of a flat-plate capacitor with a phosphor (similar to those used with fluorescent lamps) in the dielectric; it is used with alternating current. These lamps are used for night-lights and engineering applications such as luminous instrument panels.

electrolysis, process by which electric current is passed through a substance to effect a chemical change. The chemical change is one in which the substance loses or gains an electron (oxidation or reduction). The process is carried out in an electrolytic cell, an apparatus consisting of positive

electrolyte, in chemistry and physics, substance that conducts electric current as a result of a dissociation into positively and negatively charged particles called ions, which migrate toward and ordinarily are discharged at the negative and positive terminals (cathode and anode) of an electric

burn: …salts, not only disturbs their balance in the body but changes the osmotic balance of the blood and body fluids. The significance of these physiological changes was understood in 1905, but not until the 1930s were doctors able to correct them with transfusions of blood or plasma.

electrolytic cell, any device in which electrical energy is converted to chemical energy, or vice versa. Such a cell typically consists of two metallic or electronic conductors (electrodes) held apart from each other and in contact with an electrolyte (q.v.), usually a dissolved or fused ionic

conductive ceramics: Ionic conduction consists of the transit of ions (atoms of positive or negative charge) from one site to another via point defects called vacancies in the crystal lattice. At normal ambient temperatures very little ion hopping takes place, since the atoms are at relatively low…

electrolyte, in chemistry and physics, substance that conducts electric current as a result of a dissociation into positively and negatively charged particles called ions, which migrate toward and ordinarily are discharged at the negative and positive terminals (cathode and anode) of an electric

chemical analysis: Electrogravimetry: This method employs an electric current to deposit a solid on an electrode from a solution. Normally the deposit is a metallic plate that has formed from the corresponding metallic ions in the solution; however, other electrode coatings also can be formed. The use…

acid–base reaction: Hydrogen and hydroxide ions: …with the advent of the electrolytic dissociation theory propounded by Wilhelm Ostwald and Svante August Arrhenius (both Nobel laureates) in the 1880s. The principal feature of this theory is that certain compounds, called electrolytes, dissociate in solution to give ions. With the development of this theory it was realized that…