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  • electron optics
    branch of physics that is concerned with beams of electrons, their deflection and focusing by electric and magnetic fields, their interference when crossing each other, and their diffraction or bending when passing very near matter or through the spacings in its submicroscopic structure. Electron optics is based on the wave properties of electrons, which, according to quantum theory, can be treat...
  • electron pair (chemistry)
    in chemistry, an atom or a molecule that in chemical reaction seeks an atom or molecule containing an electron pair available for bonding. Electrophilic substances are Lewis acids (compounds that accept electron pairs), and many of them are Brønsted acids (compounds that donate protons). Examples of electrophiles are hydronium ion (H3O+, from Brønsted......
  • electron paramagnetic resonance (physics)
    selective absorption of weak radio-frequency electromagnetic radiation (in the microwave region) by unpaired electrons in the atomic structure of certain materials that simultaneously are subjected to a constant, strong magnetic field. The unpaired electrons, because of their spin, behave like tiny magnets. When materials containing such electrons are subjected to a strong stati...
  • electron paramagnetic resonance spectroscopy (physics)
    In a manner that is similar to that described for nuclear magnetic resonance spectrometry, electron spin resonance spectrometry is used to study spinning electrons. The absorbed radiation falls in the microwave spectral region and induces transitions in the spin states of the electrons. An externally applied magnetic field is required. The technique is effective for studying structures and......
  • electron polarization (physics)
    slight relative shift of positive and negative electric charge in opposite directions within an insulator, or dielectric, induced by an external electric field. Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. This slight separation of charge makes one side of ...
  • electron promotion
    Valence bond theory runs into an apparent difficulty with CH4. The valence-shell electron configuration of carbon is 2s22px12py1, which suggests that it can form only two bonds to hydrogen atoms, in which case carbon would have a valence of 2. The normal valence of carbon is 4, however. This......
  • electron scattering (physics)
    deflection of the path of electrons as they pass through a solid (typically a metal, semiconductor, or insulator). Deflections, or collisions, are caused by electrostatic forces operating between the negatively charged electrons and atoms within the solid (see quantum electrodynamics...
  • electron shell (chemistry and physics)
    In the quantum mechanical version of the Bohr atomic model, each of the allowed electron orbits is assigned a quantum number n that runs from 1 (for the orbit closest to the nucleus) to infinity (for orbits very far from the nucleus). All of the orbitals that have the same value of n make up a shell (see figure). Inside each shell there may be subshells corresponding to......
  • electron spectroscopy
    method of determining the energy with which electrons are bound in chemical species by measuring the kinetic energies of the electrons emitted upon bombardment of the species with X-ray or ultraviolet radiation. Details of the structure may be inferred from the results because differences in the arrangements of the atoms affect the amount of energy required to eject electrons. See also ...
  • electron spectroscopy for chemical analysis
    Since the binding energies of the electrons emitted through XPS are discrete and atoms of different elements have different characteristic electron-binding energies, the emitted electron beam can provide a simple method of elemental analysis. The specificity of XPS is very good, since there is little systematic overlap of spectral lines between elements....
  • electron spin (physics)
    To produce the ground-state electron configuration of the next element, lithium (Z = 3), one more electron is added. However, that electron cannot occupy the 1s orbital, for it has a property known as spin, which is fundamental to its behaviour. Spin is an intrinsic property of an electron, like its mass or charge. In elementary treatments, spin is often visualized as an actual......
  • electron spin resonance spectroscopy (physics)
    In a manner that is similar to that described for nuclear magnetic resonance spectrometry, electron spin resonance spectrometry is used to study spinning electrons. The absorbed radiation falls in the microwave spectral region and induces transitions in the spin states of the electrons. An externally applied magnetic field is required. The technique is effective for studying structures and......
  • electron storage ring
    Many storage rings have been constructed to study the interactions of electrons with positrons. The principal centres of this research are Cornell University; Stanford University; CERN; Tsukuba, Japan; Frascati, Italy; Beijing, China; and Novosibirsk, Russia....
  • electron structure (physics)
    the arrangement of electrons in energy levels around an atomic nucleus. According to the older shell atomic model, electrons occupy several levels from the first shell nearest the nucleus, K, through the seventh shell, Q, farthest from the nucleus. In terms of a more refined, quantum-mechanical model, the K–Q shells are subdi...
  • electron synchrotron (instrument)
    type of synchrotron designed to accelerate electrons to high energies (see synchrotron)....
  • electron transfer
    In most cases, cellular energy is generated by means of electron-transfer reactions, in which electrons move from an organic or inorganic donor molecule to an acceptor molecule via a pathway that conserves the energy released during the transfer of electrons by trapping it in a form that the cell can use for its chemical or physical work. The primary form of energy that is captured from the......
  • electron transfer chain (biochemistry)
    ...acceptor. The sugar is completely broken down to carbon dioxide and water, yielding a maximum of 38 molecules of ATP per molecule of glucose. Electrons are transferred to oxygen using the electron transport chain, a system of enzymes and cofactors located in the cell membrane and arranged so that the passage of electrons down the chain is coupled with the movement of protons (hydrogen ions)......
  • electron transfer system (biochemistry)
    ...acceptor. The sugar is completely broken down to carbon dioxide and water, yielding a maximum of 38 molecules of ATP per molecule of glucose. Electrons are transferred to oxygen using the electron transport chain, a system of enzymes and cofactors located in the cell membrane and arranged so that the passage of electrons down the chain is coupled with the movement of protons (hydrogen ions)......
  • electron transport
    ...pass down the series of oxidation-reduction reactions and in the last reaction reduce molecular oxygen (O2) to water (H2O). This part of oxidative phosphorylation is called electron transport....
  • electron trap (physics)
    ...so. The case for phosphorescence is illustrated in the Figure by B. There, interposed between the ground level and the excited level, is a level of intermediate energy, called a metastable level, or electron trap, because a transition between the metastable level and other levels is forbidden (highly improbable). Once an electron has fallen from the excited level to the metastable level (by......
  • electron tube
    device usually consisting of a sealed glass or metal-ceramic enclosure that is used in electronic circuitry to control a flow of electrons. Among the common applications of vacuum tubes are amplification of a weak current, rectification of an alternating current (AC) to direct current (DC), generation of oscillating radio-...
  • electron tunneling (physics)
    ...such states can be attained by the particle at a lower energy-content than that needed for its transfer over the top of the energy barrier, according to the classical view, this fast process of electron exchange between the electrode and a particle in solution is termed electron tunnelling through the energy barrier....
  • electron volt (unit of measurement)
    unit of energy commonly used in atomic and nuclear physics, equal to the energy gained by an electron (a charged particle carrying unit electronic charge when the electrical potential at the electron increases by one volt). The electron volt equals 1.602 × 10-12 erg. The abbreviation MeV indicates 106 (1,000,000) electron volts and GeV, 109 (1,000,000,000)....
  • electron-antineutrino (subatomic particle)
    ...through matter for a distance equal to the Earth’s diameter, reacts with a proton or a neutron. Finally, in 1956 a team of American physicists led by Frederick Reines reported the discovery of the electron-antineutrino. In their experiments antineutrinos emitted in a nuclear reactor were allowed to react with protons to produce neutrons and positrons. The unique (and rare) energy signatu...
  • electron-beam lithography
    ...sources, such as extreme ultraviolet and X-ray, are being developed to allow lithographic printing techniques to reach dimensions from 10 to 100 nanometres. Scanning beam techniques such as electron-beam lithography provide patterns down to about 20 nanometres. Here the pattern is written by sweeping a finely focused electron beam across the surface. Focused ion beams are also used for......
  • electron-beam machining
    The EBM technique is used for cutting fine holes and slots in any material. In a vacuum chamber, a beam of high-velocity electrons is focused on a workpiece. The kinetic energy of the electrons, upon striking the workpiece, changes to heat, which vaporizes minute amounts of the material. The vacuum prevents the electrons from scattering, due to collisions with gas molecules. EBM is used for......
  • electron-beam welding (metallurgy)
    In electron-beam welding, the workpiece is bombarded with a dense stream of high-velocity electrons. The energy of these electrons is converted to heat upon impact. A beam-focusing device is included, and the workpiece is usually placed in an evacuated chamber to allow uninterrupted electron travel. Heating is so intense that the beam almost instantaneously vaporizes a hole through the joint.......
  • electron-capture detector (instrument)
    ...to hydrocarbons, but it will not detect carrier gases, such as nitrogen, or highly oxidized materials, such as carbon dioxide, carbon monoxide, sulfur dioxide, and water. In another device, the electron-capture detector, a stream of electrons from a radioactive source is produced in a potential field. Materials in the gas stream containing atoms of certain types capture electrons from the......
  • electron-deficient compound
    ...different from any other class of compounds. Because the bonding in boranes involves multicentre bonding, in which three or more atoms share a pair of bonding electrons, boranes are commonly called electron-deficient substances. Diborane(6) has the following structure:...
  • electron-exchange resin
    Two separate types of resins are commonly classed as ion-exchange resins, although their functions do not involve an interchange of ions. These are the chelating resins and the electron-exchange resins. Chelating resins are styrene-divinylbenzene polymers to which iminodiacetate groups are introduced. This functional group forms complexes with all the metallic elements except the alkali metals,......
  • electron-hole pair (physics)
    ...band to the higher-energy conduction band. The electrons in the conduction band and the holes they have left behind in the valence band are both mobile and can be induced to move by a voltage. The electron motion, and the movement of holes in the opposite direction, constitute an electric current. The force that drives electrons and holes through a circuit is created by the junction of two......
  • electron-neutrino (subatomic particle)
    The basic properties of the electron-neutrino—no electric charge and little mass—were predicted in 1930 by the Austrian physicist Wolfgang Pauli to explain the apparent loss of energy in the process of radioactive beta decay. The Italian-born physicist Enrico Fermi further elaborated (1934) the theory of beta......
  • electron-nuclear double resonance (physics)
    ...other. Thus, an apparatus with two oscillating magnetic fields is employed, one for the driver and the other for the detector. Driving an NMR and detecting its effect on an ESR is known as ENDOR (electron-nuclear double resonance), whereas driving an ESR to increase a nuclear magnetization, observed by NMR, is called DNP (dynamic nuclear polarization)....
  • electron-pair bond (chemistry)
    DPin chemistry, the interatomic linkage that results from the sharing of an electron pair between two atoms. The binding arises from the electrostatic attraction of their nuclei for the same electrons. A covalent bond forms when the bonded atoms have a lower total energy than that of widely separated atoms....
  • electron-positron colliding beam
    Many storage rings have been constructed to study the interactions of electrons with positrons. The principal centres of this research are Cornell University; Stanford University; CERN; Tsukuba, Japan; Frascati, Italy; Beijing, China; and Novosibirsk, Russia....
  • electron-positron creation
    ...quanta of electromagnetic radiation. The inverse reaction γ → e+ + e− can also proceed under appropriate conditions, and the process is called electron-positron creation, or pair production....
  • electron-probe microanalyzer (instrument)
    Combinations of techniques have given rise to the scanning transmission electron microscope (STEM), which combines the methods of TEM and SEM, and the electron-probe microanalyzer, or microprobe analyzer, which allows a chemical analysis of the composition of materials to be made using the incident electron beam to excite the emission of characteristic X-rays by the chemical elements in the......
  • electron-proton storage ring
    The Hadron-Electron Ring Accelerator (HERA) at the DESY laboratory stores both electrons and protons. It is the only machine that operates in this way with particles of different masses. To do so requires two interlaced rings: one to accelerate and store the electrons, the other to accelerate and store the protons. The machine, which began operation in 1992, occupies a tunnel 6.3 km (4 miles)......
  • electron-spin resonance (physics)
    selective absorption of weak radio-frequency electromagnetic radiation (in the microwave region) by unpaired electrons in the atomic structure of certain materials that simultaneously are subjected to a constant, strong magnetic field. The unpaired electrons, because of their spin, behave like tiny magnets. When materials containing such electrons are subjected to a strong stati...
  • electronegativity (physics)
    in chemistry, the ability of an atom to attract to itself an electron pair shared with another atom in a chemical bond....
  • electroneutrality, law of (chemistry)
    The second limitation on the types of crystal structure that can be adopted by ionically bonded atoms is based on a law of physics—that the crystal must remain electrically neutral. This law of electroneutrality results in the formation of very specific stoichiometries—that is, specific ratios of cations to anions that maintain a net balance between positive and negative charge. In.....
  • electronic activation (physics)
    ...by interaction with radiation. In this energy-rich state it may undergo a variety of unusual chemical reactions that are normally not available to it in thermal equilibrium. Of special importance is electronic activation—i.e., production of an electronically excited state of the molecule (see Figure 1). This state can be reached (1) by direct excitation by photon absorption, (2) b...
  • Electronic Arts, Inc. (American company)
    American developer and manufacturer of electronic games for personal computers (PCs) and video game consoles. Established in 1982 by William M. (“Trip”) Hawkins, Electronic Arts (EA) now has a product line that includes the popular franchises The Sims, Command & Conquer, and Madden NFL...
  • electronic attraction (physics)
    ...multiplied by the other, q2, and inversely proportional to the square of the distance r between their centres. Expressed in the form of an equation, this relation, called Coulomb’s law, may be written by including the proportionality factor k as F = kq1q2/r2. In the centimetre–gram–...
  • electronic balance (measurement instrument)
    Balances of the late 20th century were usually electronic and far more accurate than mechanical balances. A scanner measured the displacement of the pan holding the object to be weighed and, by means of an amplifier and possibly a computer, caused a current to be generated that returned the pan to its zero position. Measurements were read on a digital screen or printout. Electronic weighing......
  • electronic banking system (technology)
    ...alphanumeric characters at the bottom of checks. Bank balances are computed and recorded using computer systems installed by virtually all financial institutions. Major banks have established electronic banking systems, including automatic teller machines. Located in places convenient for their customers, these automatic tellers permit users to complete basic transactions without......
  • electronic book (computing)
    Although books can be made into purely digital artifacts, “e-books” have not sold nearly as well as digital music. In part, this disparity is due to the need for an e-book reader to have a large, bright screen, which adds to the display’s cost and weight and leads to more-frequent battery replacement. Also, it is difficult to match the handy design and low cost of an old-fashi...
  • electronic bulletin board (computer science)
    ...types of face-to-face encounters such as meetings, conferences, seminars, workshops, and classroom lectures—are being supplemented and in some cases replaced by e-mail, electronic bulletin boards (a technique of broadcasting newsworthy textual and multimedia messages between computer users), and electronic teleconferencing and distributed problem-solving (a method......
  • electronic carillon (musical instrument)
    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 or other exterior site. It is played from an electric keyboard—sometimes an organ manual—acti...
  • electronic chime (musical instrument)
    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 or other exterior site. It is played from an electric keyboard—sometimes an organ manual—acti...
  • electronic commerce (computing)
    maintaining business relationships and selling information, services, and commodities by means of computer telecommunications networks....
  • electronic communication
    science and practice of transmitting information by electromagnetic means. A wide variety of information can be transferred through a telecommunications system, including voice and music, still-frame and full-motion pictures, computer files and applications, and telegraphic data. For details on the telephone and the development of telephony, see telephone. For similar information on telegraphy, se...
  • electronic communication network
    Technological developments have greatly influenced the nature of trading. By the 21st century, increased access to the Internet and the proliferation of electronic communications networks (ECNs) had allowed electronic trading, or e-trading, to alter the investment world. These computerized ECNs made it possible to match the orders of buyers and sellers of securities without the intervention of......
  • electronic conduction (physics)
    A variety of ranges of allowed and forbidden bands is found in pure elements, alloys, and compounds. Three distinct groups are usually described: metals, insulators, and semiconductors. In metals, forbidden bands do not occur in the energy range of the most energetic (outermost) electrons. Accordingly, metals are good electrical conductors. Insulators have wide forbidden energy gaps that can be......
  • electronic configuration (physics)
    the arrangement of electrons in energy levels around an atomic nucleus. According to the older shell atomic model, electrons occupy several levels from the first shell nearest the nucleus, K, through the seventh shell, Q, farthest from the nucleus. In terms of a more refined, quantum-mechanical model, the K–Q shells are subdi...
  • electronic countermeasure (military technology)
    ...part of the U.S. and Soviet nuclear forces after their deployment in 1975, 1985, and 1988, respectively. In common with all first-line combat aircraft, they were equipped with sophisticated electronic countermeasure (ECM) equipment designed to jam or deceive enemy radars. They could deliver free-fall conventional or nuclear bombs, air-to-surface missiles, and cruise missiles. The B-1B......
  • Electronic Data Systems (American company)
    ...He was commissioned in the U.S. Navy in 1953 and served until 1957, after which he worked as a salesman for International Business Machines (IBM). In 1962 Perot quit IBM and formed his own company, Electronic Data Systems (EDS), to design, install, and operate computer data-processing systems for clients on a contractual basis. EDS grew by processing medical claims for Blue Cross and other......
  • Electronic Data Systems Corporation (American company)
    ...He was commissioned in the U.S. Navy in 1953 and served until 1957, after which he worked as a salesman for International Business Machines (IBM). In 1962 Perot quit IBM and formed his own company, Electronic Data Systems (EDS), to design, install, and operate computer data-processing systems for clients on a contractual basis. EDS grew by processing medical claims for Blue Cross and other......
  • electronic database (computer science)
    any collection of data, or information, that is specially organized for rapid search and retrieval by a computer. Databases are structured to facilitate the storage, retrieval, modification, and deletion of data in conjunction with various data-processing operations. A database management system (DBMS) extracts information from the database ...
  • Electronic Delay Storage Automatic Calculator (computer)
    the first full-size stored-program computer, built at the University of Cambridge, Eng., by Maurice Wilkes and others to provide a formal computing service for users. EDSAC was built according to the von Neumann machine principles enunciated by the Hungarian American scientist John von Neumann and, like the Manchester Mark I, became operational in 1949. Wilkes...
  • electronic detection system
    ...baggage both became subject to strict scrutiny following Sept. 11, 2001. Many additional airports installed X-ray equipment, for spotting metal items in baggage or concealed in clothing, and massive electronic detection systems (EDS), which can detect trace molecules released by explosive materials. The massive weight of EDS equipment frequently requires structural modifications to existing......
  • electronic device (technology)
    branch of physics and electrical engineering that deals with the emission, behaviour, and effects of electrons and with electronic devices....
  • electronic differentiator (electronics)
    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 EOUT appearing across......
  • Electronic Discrete Variable Automatic Computer
    In 1945, with ENIAC nearing completion at the Moore School of Electrical Engineering of the University of Pennsylvania, planning began for ENIAC’s successor, the Electronic Discrete Variable Automatic Computer (EDVAC). Much, if not all, of the electrical engineering foundation for EDVAC was developed by John Mauchly and J. Presper Eckert, Jr., the Moore School faculty responsible for initia...
  • electronic eavesdropping (police science)
    the act of electronically intercepting conversations without the knowledge or consent of at least one of the participants. Historically, the most common form of electronic eavesdropping has been wiretapping, which monitors telephonic and telegraphic communication. It is legally prohibited in virtually all jurisdictions for commercial or private purposes....
  • electronic encyclopaedia
    Given the rapid pace of technological advancement in the contemporary world, it was to be expected that encyclopaedia publishers would seek ways to exploit new technologies in the field of information storage, retrieval, and distribution. During the 1960s and ’70s these new technologies revolutionized the manner in which article text was generated, modified as needed, and composed and outpu...
  • electronic energy level (molecular)
    Unlike the atom where the system is centrosymmetric (see above Foundations of atomic spectra: Basic atomic structure), the energy relationships among the nuclei and electrons in a diatomic molecule are more complex and are difficult to characterize in an exact manner. One commonly used method for consideration of the electronic energy states of a diatomic molecule is the molecular orbital (MO)......
  • electronic flash (photography)
    The most common flash system depends on a high-voltage discharge through a gas-filled tube. A capacitor charged to several hundred volts (by a step-up circuit from low-voltage batteries or from the line voltage supply) provides the discharge energy. A low-voltage circuit generating a high-voltage pulse triggers the flash, which lasts typically 11,000 second or......
  • electronic funds transfer (finance)
    Four very different types of transfer can be distinguished. First, depositors can use electronic funds transfers (EFTs) to withdraw currency from their accounts using automated teller machines (ATMs). In this way an ATM withdrawal works like a debit card. ATMs also allow users to deposit checks into their accounts or repay bank loans. While they do not replace the assets used as money, ATMs......
  • electronic game
    any interactive game operated by computer circuitry. The machines, or “platforms,” on which electronic games are played include general-purpose shared and personal computers, arcade consoles, video consoles connected to home television sets, and handheld game machines. The term video game can be used to represent the totality of these formats, or it ca...
  • electronic instrument (music)
    any musical instrument that produces or modifies sounds by electric, and usually electronic, means. The electronic element in such music is determined by the composer, and the sounds themselves are made or changed electronically. Instruments such as the electric guitar that generate sound by acoustic or mechanical means but that amplify the sound electrically or electronically a...
  • electronic integrator (electronics)
    ...adjusted for the detector response factor for that solute, is proportional to the amount of solute producing the peak. The area is frequently approximated from the peak width and height. 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......
  • electronic log (instrument)
    ...When the ship is moving, pressure in the forward-facing tube exceeds the pressure in the side tubes; this differential is transmitted to equipment that translates it into a speed measurement. In the electronic log, which also protrudes through the bottom of the ship, a water-driven rotor turns a small electric generator, the current from which is proportional to the speed of the ship. This......
  • electronic mail (computer science)
    messages transmitted and received by digital computers through a network. An e-mail system allows computer users on a network to send text, graphics, and sometimes sounds and animated images to other users....
  • electronic mail system (postal system)
    ...or chartered aircraft. New services based on communications and computer technology have been introduced. The Intelpost facsimile service operates nationally and with many other countries. An electronic mail system enables data for large mailings to be transmitted to local centres for enveloping and delivery....
  • electronic monitor (penology)
    ...a corporate board; a corrupt politician may be blocked from holding future public office; and parents who abuse their children may be deprived of parental rights. Finally, new technologies, such as electronic monitoring through ankle bracelets and other surveillance devices, have allowed probation and parole officers to restrict the movement of offenders who live in their own homes or in......
  • electronic music
    any music involving electronic processing, e.g., recording and editing on tape, and whose reproduction involves the use of loudspeakers....
  • Electronic Numerical Integrator and Computer (computer)
    the first programmable general-purpose electronic digital computer, built during World War II by the United States. In the United States, government funding during the war went to a project led by John Mauchly, J. Presper Eckert, Jr., and their colleagues at the Moore School of Electrical Engineering at the University of Pennsylvania; their ...
  • electronic organ (musical instrument)
    keyboard musical instrument in which tone is generated by electronic circuits and radiated by loudspeaker. This instrument, which emerged in the early 20th century, was designed as an economical and compact substitute for the much larger and more complex pipe organ....
  • electronic oven
    appliance that cooks food by means of high-frequency electromagnetic waves called microwaves. A microwave oven is a relatively small, boxlike oven that raises the temperature of food by subjecting it to a high-frequency electromagnetic field. The microwaves are absorbed by water, fats, sugars, and certain other molecules, whose consequent vibrations produce heat. The heating thus occurs inside the...
  • electronic paper
    PARC continued to develop new ideas and technologies through the 1990s, but they were tethered to the Xerox mission of being The Document Company®. Among the most interesting innovations was electronic paper, a flexible, reusable plastic material containing millions of charged bichromal beads suspended in individual oil-filled cavities. As designed by inventor Nick Sheridon, each bead could...
  • electronic phototypesetter
    In phototypesetters of the third generation, the beam of light is replaced by a flow of electrons, which offers the advantage that the electrons can be deflected by means of magnetic fields without the intervention of mechanical parts such as mirrors and lenses. Television systems are based on this characteristic, and an early type of electronic phototypesetter is structurally comparable to a......
  • electronic polarization (physics)
    slight relative shift of positive and negative electric charge in opposite directions within an insulator, or dielectric, induced by an external electric field. Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. This slight separation of charge makes one side of ...
  • electronic publishing
    The Internet has become an invaluable and discipline-transforming environment for scientists and scholars. In 2004 Google began digitizing public-domain and out-of-print materials from several cooperating libraries in North America and Europe, such as the University of Michigan library, which made some seven million volumes available. Although some authors and publishers challenged the project......
  • electronic sound synthesizer
    machine that electronically generates and modifies sounds, frequently with the use of a digital computer. Synthesizers are used for the composition of electronic music and in live performance....
  • electronic specific heat (physics)
    ...the lattice vibrations (an amount that is the same for a system in the normal and in the superconducting state), and the remainder is used to increase the energy of the conduction electrons. The electronic specific heat (Ce) of the electrons is defined as the ratio of that portion of the heat used by the electrons to the rise in temperature of the system. Figure 1......
  • electronic structure (physics)
    the arrangement of electrons in energy levels around an atomic nucleus. According to the older shell atomic model, electrons occupy several levels from the first shell nearest the nucleus, K, through the seventh shell, Q, farthest from the nucleus. In terms of a more refined, quantum-mechanical model, the K–Q shells are subdi...
  • electronic substrate ceramics
    advanced industrial materials that, owing to their insulating qualities, are useful in the production of electronic components....
  • electronic switching (communications)
    As telephone traffic continued to grow through the years, it was realized that large numbers of common control circuits would be required to switch this traffic and that switches of larger capacity would have to be created to handle it. Plans to provide new services via the telephone network also created a demand for innovative switch designs. With the advent of the transistor in 1947 and with......
  • electronic switching system (communications)
    Between 1960 and 1962 AT&T conducted a field trial of an electronic switching system (ESS) that employed a variety of new devices and concepts. Among these innovations was a gas-tube crosspoint network to perform the actual switching function. In order for a particular switch to close or make a connection, a high voltage was applied to a gas-filled tube, causing the gas to ionize and......
  • electronic system (technology)
    branch of physics and electrical engineering that deals with the emission, behaviour, and effects of electrons and with electronic devices....
  • electronic trading (finance)
    The past few years have seen a spectacular and revolutionary development in the mechanics of stock trading—perhaps the largest change since brokers’ fees were deregulated in 1975—electronic trading, or “e-trading.” Sleek names of on-line firms like Ameritrade, Charles Schwab, and E*Trade are being bandied about more than old-line composite brok...
  • electronic voltmeter (instrument)
    ...to measure voltage directly rather than by the effect of current. The potentiometer operates by comparing the voltage to be measured with known voltage; it is used to measure very low voltages. The electronic voltmeter, which has largely replaced the vacuum-tube voltmeter, uses amplification or rectification (or both) to measure either alternating- or direct-current voltages. The current needed...
  • electronic voting
    a form of computer-mediated voting in which voters make their selections with the aid of a computer. The voter usually chooses with the aid of a touch-screen display, although audio interfaces can be made available for voters with visual disabilities. To understand electronic voting, it is convenient to consider four basic steps in an election process: ballot composition, in which voters make choi...
  • electronic watch
    ...pulses. Each oscillation of the balance operates a time-indicating gear train by advancing a toothed wheel one tooth. First produced in 1953, the resonance drive type, properly called an electronic watch, is inherently more accurate since it operates at a frequency higher than that customarily used with balance-type watches, and the tuning fork is a fairly stable source of frequency.......
  • electronic work function (physics)
    energy (or work) required to withdraw an electron completely from a metal surface. This energy is a measure of how tightly a particular metal holds its electrons—that is, of how much lower the electron’s energy is when present within the metal than when completely free. The work function is important in applications involving electron emission from metals, as in ph...
  • electronic-grade silicon (electronics)
    an assembly of electronic components, fabricated as a single unit, in which miniaturized active devices (e.g., transistors and diodes) and passive devices (e.g., capacitors and resistors) and their interconnections are built up on a thin substrate of semiconductor material (typically silicon...
  • electronically scanned phased array (radar)
    ...elemental dipole are in unison, or in step. (The radar engineer would say that the signals are “in phase” with one another or that they are coherently added together.) This is called a phased-array antenna....
  • electronically steered phased array (radar)
    ...elemental dipole are in unison, or in step. (The radar engineer would say that the signals are “in phase” with one another or that they are coherently added together.) This is called a phased-array antenna....
  • electronics
    branch of physics and electrical engineering that deals with the emission, behaviour, and effects of electrons and with electronic devices....
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