This glossary of electrical and electronics engineering is a list of definitions of terms and concepts related specifically to electrical engineering and electronics engineering. For terms related to engineering in general, see Glossary of engineering.
A
AC adapter An external power supply for portable devices that allows them to operate from wall-socket electricity.
AC power plugs and sockets Electrical connectors used with alternating current.
AC power Electric power where the current reverses direction periodically.
AC-to-DC conversion (rectifier) Rectification of AC current, so that current flows in only one direction.
AC-to-AC converter A power converter where the input and output are both in the form of alternating current (AC), but may differ in frequency or other characteristics.
AC/DC receiver design A radio receiver that can operate from either alternating current or direct current wall socket power.
active rectification A circuit where rectifier devices are externally controlled to change AC to current flowing in one direction.
actuator An end device of a control system that manipulates a physical variable such as a valve opening or the position of a machine part.
adaptive control A control strategy where parameters are adjusted as the controlled process changes.
additive white Gaussian noise A noise model that is used in telecommunications to model the effects of various random processes.
adjustable-speed drive Control for a motor that allows more than one speed to be selected.
advanced z-transform A mathematical technique used to model and analyze digital systems.
affinity laws Mathematical formulas that relate the speed, flow, and diameter of pumps, fans, blowers, and turbines, useful for predicting output under varying conditions.
agbioeletric A brand name of a kind of vegetable oil for use in transformers.
AIEE American Institute of Electrical Engineers, predecessor organization to IEEE.
alpha–beta transformation A mathematical technique useful in analysis of three-phase circuits.
alternating current (AC) Electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows in only one direction.
alternator An electrical machine that converts mechanical power into AC electric power.
alternator synchronization The process of synchronizing an alternator to a grid or to another alternator.
aluminium smelting The reduction of aluminium ore to metal, by use of large amounts of electric power.
ammeter An instrument that measures electric current.
amorphous metal transformer A power transformer where the metallic core is made of metals cooled so quickly that they do not form a crystal structure; such transformers can reduce some kinds of energy loss.
ampacity The current-carrying capacity of a conductor, in the context of electric power wiring.
ampere (A) Also amp. The SI unit of electric current, equal to one coulomb (C) passing a given point in an electrical circuit per second.
Ampère's circuital law Also simply Ampère's law or Oersted's law. The mathematical relation between the integral of the magnetic field over some closed curve to the current passing through the region bound by the curve.
Ampère's force law The mathematical relation between the force between two current-carrying conductors and the current flowing in them.
Ampère's law See Ampère's circuital law.
amplidyne An electric machine that allows a small current to control a much larger current.
amplifier A system that produces an output that replicates an input signal but with a larger magnitude.
amplitude modulation Transmission of information by changing the magnitude of a carrier signal, for example sending sound by radio.
analog circuit A circuit where currents and voltages vary continually within some practical range, in proportion to some signal.
analog filter An analog circuit that alters some frequency-related property of a signal.
analog signal processing Generally, techniques used to alter signals that rely on voltages or currents that vary continually over a practical range.
analog signal A signal whose properties (current, voltage) vary proportionally to the information transmitted.
analog-to-digital converter A circuit that produces a number proportional to the magnitude of a voltage or current.
anode The terminal of an electrochemical or electronic device through which conventional current flows inward.
antenna A structure which converts between electromagnetic waves in space and currents in a conductor.
apparent power In an alternating current power circuit, the product of the magnitude of RMS voltage and current.
Apple Inc. (formerly known as Apple Computer) A company that makes mobile telephones and computers.
arbitrary waveform generator A type of signal generator that can generate almost any waveform.
arc converter A device once used to generate radio waves.
arc furnace A furnace that melts materials with the intense heat produced by an electric arc.
arc lamp An electric lamp that generates visible light from an electric arc.
arc welder A device used to join metals by melting them with the intense heat produced by an electric arc.
armature That part of an electrical machine that converts electrical energy to mechanical energy (or vice versa).
artificial intelligence (AI) A computer system that replicates some feature of human intelligence.
artificial neural network A network of individual logic elements in multiple layers that mimics the functions of a biological nervous system; a technique in artificial intelligence.
asymptotic stability A condition of a control system where the output eventually reaches a steady-state value in response to any input.
asynchronous circuit A digital circuit where states propagate through a circuit without a synchronizing clock impulse.
audio and video connector An electrical fitting used to connect cables carrying audio or video signals.
audio equipment Equipment used to handle signals at frequencies within the human range of hearing.
audio filter A circuit intended to alter some frequency-related property of a signal carrying sound information.
audio frequency A signal whose frequency is within the range of human hearing.
audio noise reduction Reduction of interfering signals in an audio signal.
audio signal processing Alteration of any properties of a signal carrying sound information (dynamic range, frequency response, or others).
audion tube An early three-electrode vacuum tube that had amplifying properties.
Austin transformer A kind of isolation transformer.
automatic gain control A circuit that automatically adjusts the magnitude of a signal to prevent it from becoming too small or too large.
automatic transfer switch An electrical switch used to automatically select a standby source of electrical power when the principal source is lost.
automation Automatic control of a process.
autorecloser A circuit protection device for overhead power distribution lines which briefly interrupts a circuit when a fault is detected, then restores the circuit in the expectation the fault has cleared.
autotransformer A transformer where the primary and secondary circuits share some of the transformer windings.
availability factor The fraction of time that a power plant is available to produce power.
avalanche diode A diode intended for regular operation in the reverse, avalanche breakdown, mode. Used as a voltage reference, noise source, and in certain classes of microwave oscillator device.
average rectified value The average value of an alternating current waveform, taking the absolute value of the waveform. The average value is generally different from the root-mean-square value.
B
backward wave oscillator A type of micowave oscillator vacuum tube.
balanced line A transmission line with two conductors, with equal impedances to earth ground.
ball bearing motor A conceptual motor that does not use electromagnetism.
balun A device that connects a balanced transmission line to an unbalanced line.
band-pass filter A filter that lets through signals within a range of frequencies.
band-stop filter A filter that blocks signals with a particular range of frequencies.
bandwidth The range of frequencies over which a system generates or uses significant signal power.
bang-bang control A controller that switches a final element on or off instead of providing a proportional response.
Barlow's wheel A demonstration of electromagnetic principles.
Bartlett's bisection theorem A mathematical theorem used in network analysis.
base load power plant An electric power plant that furnishes the part of the load that does not vary during a day.
battery An electrochemical device that produces electric power from chemical reactions.
battery eliminator An AC adapter, which allows battery operated equipment to run on wall-socket AC power.
Bayer filter An optical filter used in color digital cameras.
beam tetrode A type of vacuum tube with four active elements plus a pair of beam forming plates.
beat frequency A frequency produced by non-linear mixing of signals at two other frequencies.
Bell Telephone Laboratories Formerly, the research and development laboratory of the American Telephone and Telegraph Corporation.
biasing The practice of setting the quiescent operating conditions of an amplifying device to obtain desired response.
BIBO stability A control system that produces finite outputs for any finite input.
bilinear transform A mathematical technique to obtain the parameters for a digital filter to duplicate the response of some analog filter transfer function.
bimetallic strip A temperature-sensing element made of two metals that have different coefficients of expansion which have been intimately bonded together.
Biot–Savart law The mathematical relationship between a magnetic field and the current producing that field.
bipolar junction transistor A type of transistor with two kinds of charge carriers.
blocked rotor test A test of an electric machine where the machine is energized but the shaft is prevented from turning.
Blu-ray A type of optical disc written and read using a blue/violet laser.
Bode plot A plot of the amplitude and phase frequency response of a system, where the actual response is approximated by straight-line segments.
Boolean algebra A type of algebra that deals with values that can only hold values "true" and "false", of great use in design and analysis of digital systems.
boost converter Any power converter circuit that can produce an output voltage larger than its input voltage.
booster A device used to increase voltage on an electric power distribution system, such as a motor-generator set on a DC system.
bound charge Electric charge in a material that is not free to move through the material.
braking chopper A device used to absorb energy from a motor to slow it down.
branch circuit In building wiring, any circuit from the main panelboard to utilization equipment or receptacles.
breakdown voltage The maximum voltage a device can withstand without damage.
bridge rectifier A set of rectifier diodes used to convert alternating current to direct current.
broadcasting Transmission of a signal to many receivers.
brush A sliding electrical contact between a moving part and a stationary part.
brushed DC electric motor An electric motor with brushes.
brushless DC electric motor An electric motor without brushes.
Buchholz relay A gas pressure sensing device for protection of oil-filled transformers.
Buck converter Any power converter circuit that produces an output voltage less than its input voltage.
Buck–boost converter Any power converter circuit that can provide a voltage greater or less than its input voltage.
Buck–boost transformer A transformer that can be used to adjust voltage.
busbar A set of conductors used to distribute current to many branches.
bushing An electrical fitting used to connect external conductors to the interior of apparatus.
Butterworth filter A type of filter with the flattest possible pass band.
buzzer An electromechanical or electronic device that produces a sound when energized.
C
Canadian Electrical Code The technical standard for building wiring in Canada.
Canadian Standards Association Non-profit organization that develops electrical and other technical standards.
capacitance The ability of a body to hold an electrical charge.
capacitor An electrical component that stores energy in an electric field.
capacitor-input filter A power supply network where a capacitor is the first element following the rectifier.
capacitor voltage transformer In electrical power systems, an instrument transformer for measuring voltage that uses a capacitive voltage divider.
capacity factor The ratio of energy produced by a power plant over some period, over its maximum possible energy production in that time.
carrier current A system for communications where a carrier signal is impressed on power line wiring.
carrier wave A radio wave that can be modulated (changed systematically) to carry information to a receiver.
Category 3 cable A performance standard for unshielded twisted pair cables for analog voice and low speed data circuits within a building.
Category 5e cable A performance standard for unshielded twisted pair cables for telephone and data within a building.
Category 6 cable A performance standard for unshielded twisted pair cables for telephone and high speed data within a building.
catenary A geometric form of curve, the shape of a uniform cable hanging between two supports.
cathode ray oscilloscope An electronic instrument that displays the wave shape of electrical signals on a cathode ray tube.
cathode ray tube A vacuum tube that relies on an electron beam – usually used to render images on a fluorescent screen such as in television sets.
cathode The terminal of an electrochemical or electronic device from which conventional current exits the device.
cat's-whisker detector A radio detector that uses a manually-set "whisker" contact to a crystal of galena or other material, to form a rectifying junction.
CATV Cable television, distribution of television programming over a wire instead of by radio broadcast.
cavity magnetron A vacuum tube that is a high power microwave oscillator, using a resonant cavity and electrons traveling through a magnetic field.
CD A "Compact Disc" used to store digital data or digitally recorded sound using an infrared laser.
center tap A connection on a transformer which has equal voltage to either end of the transformer winding.
ceramic resonator A piezoelectric element used to stabilize the frequency of an oscillator.
channel Any communication path between a signal transmitter and a signal receiver, or, a pre-selected operating frequency for a radio system.
channel capacity An upper bound on the rate at which information can be reliably transmitted over a communication channel.
charactron A kind of text display vacuum tube that used an internal element to shape an electron beam to represent the shape of letters and other symbols.
charge pump A DC to DC converter circuit that uses capacitors to store energy between stages.
charge transfer switch A kind of charge pump circuit.
charge-coupled device An imaging sensor or data storage device that represents a signal, or pixel, by the charge stored in a capacitor and is able to move that charge from one capacitor to the next.
Chebyshev filter A form of filter that has a steep frequency selective characteristic.
choke An induction coil used to block alternating current and pass direct current, or to block high frequencies and pass lower frequencies.
chopper A circuit that switches on and off at a high rate, used either for power conversion or to convert a DC signal to a more easily processed AC signal.
circle diagram A representation of the voltage and current characteristics of an electrical machine; the plot traces out a circle or part of a circle.
circuit breaker panel A distribution board for electric power that uses circuit breakers as protective elements.
circuit breaker An automatically operated electrical switch that opens to interrupt a short circuit or other fault.
circuit theory The mathematical theory of electrical circuits.
Circuit Total Limitation (CTL) A US National Electrical Code rule for the number of circuits in a panel board.
clamp meter An ammeter that measures current with a split core that can be clamped on a wire.
Clapp oscillator An electronic oscillator circuit that uses three capacitors and an inductor.
class of accuracy in electrical measurements A measure of the error produced by an electrical measuring instrument.
closed-loop controller Any controller that manipulates some process variable to minimize the difference between the current state of the variable and the desired set point, such as temperature, flow, or others.
CMOS Complementary metal–oxide–semiconductor, a fabrication process for MOSFETs and integrated circuits
coaxial cable A cable with an inner conductor centered inside a flexible tubular conductor, used for radio frequency transmission lines.
Cockcroft–Walton generator A kind of circuit for generating very high DC voltage.
cogeneration Production of electricity along with some other desired product, such as process steam or desalinated water.
cold cathode An element of a vacuum tube that emits electrons without a heating circuit.
Colossus A British code breaking system used during World War II.
combined cycle A thermal power plant that improves efficiency with two different kinds of energy extraction from the combustion products gas stream, such as a gas turbine followed by a steam boiler.
communication system A system intended to convey information from one place to another with an expected degree of performance.
communications satellite A satellite in Earth orbit designed for international telephone, television, or data transmission.
commutation cell The elementary switching device in a power converter circuit; it could be a transistor, a thyristor, a mercury-arc valve, or others.
commutator A component of a DC electric machine that connects the rotating coils with an external circuit through brushes.
compact fluorescent lamp A fluorescent lamp with a folded or spiral tube, designed to fit in the same space as an incandescent lamp of similar light output.
Compactron A brand of vacuum tube, used in some radio and television sets, that combined multiple independent functions in one envelope.
compensation winding A winding on a motor or generator to improve commutation at heavy load.
computed tomography Production of images of a cross-section through an object by multiple X-ray measurements processed in a computer.
computer engineering The profession of designing computers.
computer hardware That part of a computer system with physical existence.
computer programming The practice of producing instructions for a computer to achieve some desired effect.
computer-aided design (CAD) A design discipline where a computer is used to produce a graphical representation of a real-world object in order to design its structure or to assist in calculating performance parameters.
conduction band In a conductor, the energy levels of charge carriers that are free to move through the material.
constant k filter A method formerly used for designing filters for a required characteristic.
consumer electronics Electronic devices intended to be owned by consumers directly; a mobile cell phone is "consumer electronics" but the cell site it communicates with is not.
contactor An automatically controlled electrical switch (relay), used to operate motors or other high-current loads.
continuous Fourier transform A mathematical operation that expresses a signal in time as the sum of its frequency components.
continuous signal A signal that can take any value within its range.
control engineering The application of control theory to practical problems.
control system The equipment used to adjust some parameter of an ongoing process to regulate its behavior to a desired goal, such as positioning a disk drive head or regulating temperature of a furnace.
control theory The mathematical study of behavior of control systems.
controllability In control theory, the degree to which a system can be put into any desired state given manipulation of one variable.
controller A system that adjusts some variable to control a process.
copper cable certification The process of testing a computer network cable installation to verify that it meets standards.
copper loss That portion of an electric machine or transformer's loss attributed to the resistance of conductors (which are not necessarily made of copper).
corona ring A component of a high-voltage system intended to smooth out the electric field distribution around energized parts.
coulomb The SI unit of electric charge.
Coulomb's law The mathematical relation between force, electric charge and distance.
CPU Central Processing Unit, the element of a computer that carries out arithmetic and logic operations.
crest factor The ratio of peak to effective (RMS) value of a waveform.
crossed-field amplifier A type of microwave amplifier vacuum tube.
crosstalk Objectionable presence of a signal from one circuit in another circuit sharing the same transmission path, such as a cable.
crystal oscillator An electronic oscillator whose frequency is stabilized by a piezoelectric crystal resonator element.
Ćuk converter One kind of buck-boost voltage converter that uses a capacitor as an energy storage element.
current The movement of electric charge.
current density The current flowing per unit area of a conductor.
current source inverter A type of power inverter where an inductor tends to keep a constant current flowing in the inverter stage.
current source In circuit theory, an element that produces a defined current independent of the connected circuit properties.
current transformer An instrument transformer used for measuring current in AC power systems.
current-to-voltage converter A transducer that produces an output voltage in response to an input current.
cybernetics The science of automatic control systems.
cycloconverter A type of variable-frequency power converter that does not first convert AC to DC.
D
damping ratio A parameter that indicates how rapidly oscillations in a system die out, if ever.
Darlington transistor An interconnection of two transistors to provide a gain that is the product of the individual gains.
data compression Any technique that allows information to be transmitted more compactly than originally expressed, for example, codes.
data networks A network for interconnection of computers and peripherals.
DC injection braking A method of slowing an AC electric motor by passing direct current through its windings.
DC-to-DC converter A circuit that converts a DC voltage into a different level of DC voltage.
degaussing The process of reducing the residual magnetic field in a metallic object, such as a ship.
delay line A circuit component that introduces a delay in a signal.
delta-wye transformer One type of connection of a three-phase transformer.
demand factor The fraction of actual use of some quantity, related to the maximum that could be used in a specified time.
demand response The ability of a generating station or grid to follow changes in load while maintaining voltage and frequency within acceptable limits.
demodulation The process of recovery of information (sound, video, data) from a modulated carrier.
describing function A method for analyzing non-linear control systems.
detector A circuit that demodulates a radio signal to recover information.
DIAC A four-layer semiconductor diode that has a predictable breakdown characteristic.
dielectric A material that does not allow free flow of electric current.
digital audio broadcasting Transmission of sound by digital signals over radio.
digital circuit A circuit where all points on the signal path have only one of two states.
digital computers A computer made of digital circuits.
digital control A control system that processes signals in digital form.
digital filter A filter implemented as a digital circuit.
digital image processing Manipulation of an image by a digital computer.
digital micromirror device An element of a kind of digital projector system.
digital protective relay A power system protection device that processes signals in digital form.
digital signal controller A type of microprocessor that combines a digital signal processor element with a more general purpose microcontroller.
digital signal processing The technique of modifying the properties of a signal that has been converted to digital form.
digital television Transmission of images using digital techniques.
digital-to-analog converter A device that produces a voltage or current that is proportional to a digital value sent to it.
diode bridge An interconnection of diodes to rectify alternating current to direct current.
diode A two-terminal passive circuit element, with a preferred direction of current flow.
dipole antenna A simple form of antenna that consists of two conductors oriented end-to-end with a feed in between them.
direct current (DC) Also galvanic current. Electric current that flows in one direction only, in contrast to alternating current (AC), where the flow of current periodically changes direction and magnitude.
direct on line starter A kind of motor starter that does not reduce the voltage at the motor terminals.
direct torque control A method of estimating motor torque as part of a variable speed motor drive.
discrete cosine transform A mathematical technique for representing a sampled signal as a sum of cosine waves of different frequencies.
discrete Fourier transform A mathematical technique for representing a sampled signal as a sum of sine and cosine waves of different frequencies.
discrete-time signal A signal represented as a time series of samples taken at regular intervals.
displacement current The effect of a time-varying electric field, which induces a magnetic field just as the motion of electrical charges does.
display device Any device that displays data from an information system, such as a watch readout or an automatic scoreboard.
dissipation The loss of energy in a system, such as dielectric loss in a capacitor.
dissolved gas analysis A technique for fault detection in oil-filled transformers.
distributed control system A control system in which significant parts of the control process are decentralized.
distributed-element model An analysis of an electric circuit where capacitance, inductance, and resistance are distributed along the circuit, as in a transmission line, not concentrated in lumped components.
distributed generation An electrical grid where multiple small sources contribute energy, instead of relatively few large central generating stations.
distribution board A piece of electrical switchgear which distributes electric power to multiple branch circuits.
distribution transformer A power transformer, usually used to change the utility distribution voltage to a lower voltage for use on the customer premises.
Dolby A trademark for a noise reduction technique for analog sound recordings.
dot convention A system for marking terminals on instrument transformers to maintain correct polarity.
doubly fed electric machine An electric machine where both moving and stationary elements have external connections handling significant power.
downsampling A technique for reducing the number of signal samples processed by a digital system; decimation.
Dqo transformation A technique used to simplify mathematical analysis of polyphase electric circuits.
droop speed control A method of regulating generators so that multiple units share the load proportional to their ratings.
dual control theory A branch of control theory that deals with systems whose characteristics are initially unknown.
dual loop A method of supervising contacts and wiring in a security system, so as to detect some faults or tampering.
DVD Digital Versatile Disc, a type of optical disc for distributing video recordings and data using an orange/red laser.
dynamic braking A braking system that extracts energy from a moving system to bring it to rest; a dynamic braking system generally is not used to hold a position of a stationary object.
dynamic demand A technique for load management on an electrical grid based on frequency measurement.
dynamic programming A technique for optimization of the solution of a problem by combining solutions to smaller sub-problems.
dynamic random-access memory A type of semiconductor memory where data is stored as electric charges on capacitors; the charges must be refreshed periodically or else they will leak away, losing the stored data.
dynamo A direct-current generator, whose exciting field is provided by an electromagnet.
E
earth-leakage circuit breaker (ELCB) A protective device consisting of a current- or voltage-sensing mechanism that opens or "breaks" a circuit when stray current or voltage is detected, which might otherwise present the possibility of electric shock.
eddy current An electric current induced inside a conductor exposed to a changing magnetic field.
edge detection An image processing technique used to identify boundaries of objects.
Edison effect Also thermionic emission. The emission of an electric current from a hot electrode, the thermal energy of which gives some small charged particles such as electrons and ions enough kinetic energy to escape the material's surface. Thermionic emission is the fundamental mechanism underlying the vacuum tube.
electret A dielectric material that quasi-permanently retains an impressed electrical polarization; the dual to a magnet.
electric arc The discharge of electric current through an open space between conductors, either intentionally to produce a source of intense light and heat, or as the result of an electrical fault.
electric charge The physical property of matter that causes it to experience a force when placed in an electromagnetic field.
electric circuit A closed path through which an electric current can flow.
electric current The motion of electric charges.
electric displacement field In Maxwell's equations, a vector field due to electric charges.
electric distribution systems That portion of an electrical grid that connects customers to substations or the bulk transmission system.
electric field gradient (EFG) The rate of change of an electric field with respect to distance.
electric field A vector field that exerts a force on electric charges.
electric generator A machine that converts mechanical energy to electrical energy by moving conductors through magnetic fields.
electric motor A machine that produces mechanical energy from electrical energy, by moving conductors through magnetic fields.
electric multiple unit The use of more than one electric locomotive on a train.
electric potential A measure of the work required to move a unit electric charge in an electric field.
electric power conversion Generally, changing the form of electric power.
electric power distribution In an electric grid, the network that brings power from a substation or bulk supply to individual customers.
Electric Power Research Institute A non-profit organization that carries out research on behalf of the US electric power industry.
electric power transmission The bulk movement of electric power for many customers from a generating plant to a local distribution network, usually at high voltage.
electric power The rate of transfer of electrical energy past a given point.
electric shock An injury caused to people or animals by electric current.
electrical cable A flexible conducting wire to carry electrical power or signals, usually covered with an insulating material.
electrical code A set of regulations for the use of electricity; they may vary from municipal to international in scope.
electrical conductivity A measure of a substance's ability to pass an electric current.
electrical conductor An object that carries an electric current, with little loss.
electrical contact A separable part of an electric device that carries current when touching another contact.
electrical discharge machining (EDM) Shaping of a workplace by small sparks.
electrical element In circuit theory, a node at which some electrical property is concentrated (resistance, etc.).
electrical engineering The profession of applying electricity to practical problems.
electrical equipment Any apparatus for generation, transmission or utilization of electric power.
electrical grid A geographically distributed system to connect sources and users of electric power.
electrical impedance That property of a circuit that resists the passage of electric current, usually in the context of alternating current.
electrical insulation paper A grade of paper used for insulation of transformers, electrical machines, capacitors, and some cables.
electrical insulation A material that resists electrical current flow.
electrical load A consumer of electrical energy, turning it into light, heat, mechanical power, data, or chemical changes.
electrical machine Any apparatus that converts between electrical power and mechanical power, such as a motor or generator.
electrical measurements That branch of metrology concerned with electrical quantities.
electrical network A network of electrical components and conductors.
electrical polarity Identification of electrical terminals where current is flowing in the same direction relative to the device.
electrical steel Any of several types of steel used for manufacturing the magnetic field components of machines and transformers.
electrical substation A facility connecting a distribution network to a transmission network, usually with one or more transformers.
electrical technologist A specialist in applying electrical theory and technique to practical problems.
electrical wiring regulations The legal framework for electrical installations in buildings.
electrical wiring The installation of conductors, fixtures and protection devices for a structure or vehicle.
electricity meter An instrument to measure the electrical energy used by a customer for revenue purposes.
electricity pylon A structure, generally of wood or metal, to support wires.
electricity The set of physical phenomena associated with electric charges.
electrification Applying electric power to a process that was previously done by other means, or, development of an electric power system in a region that previously had none.
electroactive polymers A polymer that significantly changes size or shape when exposed to an electric field.
electrocardiograph A record of the electrical activity of the heart.
electrochemical engineering The profession of application of electrochemistry to practical problems.
electrode An electrical contact that connects some medium to an electric circuit, such as in an electrochemical cell or a vacuum tube.
electro-diesel locomotive A railway locomotive with a diesel engine, generator, and electric driving motors that can be powered by the diesel engine or the track electrical supply.
electrodynamics The branch of physics that studies electrical charges and electrical currents.
electrolyte A liquid or solid medium that carries electric current in the form of ions.
electromagnet A magnet that generates a magnetic field from an electric current.
electromagnetic compatibility The control of unwanted electromagnetic interference.
electromagnetic field The field produced by moving electric charges and magnetic fields.
electromagnetic induction The production of current in a circuit by the change of magnetic field intersecting the circuit.
electromagnetic radiation Radio waves, light and other radiation that travels through space at the speed of light.
electromagnetic spectrum The range of frequencies of electromagnetic radiation.
electromagnetic wave equation A second-order partial differential equation that describes the propagation of electromagnetic waves through a medium or in a vacuum.
electromagnetism The science of electric fields, magnetic fields, currents, charges, and forces.
electromechanical A system that has both an electrical component and a mechanical component, such as a motor or a relay.
electromote An 1882 demonstration of a prototype electric trolley bus.
electromotive force A difference in electrical potential between two points, such as produced by a battery or a generator.
electron microscope An instrument that provides highly magnified images by use of an electron beam.
electronic amplifier A device that increases the power of an electrical signal by electronic means.
electronic circuit A circuit using one or more electronic devices.
electronic component An active or passive element of an electronic circuit.
electronic control unit In an automobile, an embedded electronic system that controls some aspect of a vehicle (ignition, transmission, and so on).
electronic design automation A system in which a computer provides assistance to the designer of a device or system.
electronic engineering The profession of applying electronics to practical problems.
electronic filter A filter that alters some frequency-related characteristic of a signal.
electronics The study of the flow of electrons through a vacuum, gases, or semiconductors.
electronic speed control A device for regulating the speed of a motor.
electrophorus An instrument used to produce electrostatic charge through electrostatic induction.
electrostatic motor A motor that relies on the forces generated by electric fields, instead of magnetic fields.
electrostatics The study of stationary electric charges and resulting forces.
embedded operating system The common operating environment that supports embedded software; it may be a highly tailored version of a general-purpose operating system, or written solely for the purpose of embedded system operations.
embedded software A firmware component of a microprocessor-controlled system.
embedded system A computer system that controls a device or system, with no or a minimal user interface; for example, the ignition system in a car may have a microprocessor to control it.
enameled wire Wire insulated with a thin flexible layer of enamel, used for electrical windings.
energy demand management A system to adjust energy demand to reduce costs.
energy economics A branch of economics concerned with energy supply and demand.
energy efficient transformer A power transformer designed to have lower than average energy loss.
energy returned on energy invested A measure of how long an energy producing system takes to replace the energy it took to make it.
energy subsidies Payments to a consumer or producer of electric energy that are used as incentives for production or consumption.
engine-generator A combination of an internal combustion engine and a generator, often used as a standby power plant.
ENIAC The first general purpose electronic digital computer.
Epstein frame An apparatus used for testing of magnetic materials.
equalization 1. (audio) The adjustment of the frequency response of an audio system to improve its utility. 2. (communications) The adjustment of the frequency spectrum of a communications signal to cancel out the effect of the frequency response of a communication path.
equivalent circuit In circuit theory, a simple combination of elements that behaves at its terminals like a more complex combination.
equivalent impedance transforms A mathematical method to determine values of an equivalent circuit.
error correcti