Abbreviations, Terms and Definitions in Electricity and Electronics

Microampere (sometimes ua)


Microvolt (sometimes uv)


Abbreviation for "ampere" a unit of electrical current.

A (amp)



Analog to digital


Loss or dissipation of energy as it travels through a medium, Example: radio waves lose some of their energy as they travel through the atmosphere.


 Automatic bus transfer


Alternating current


Alternating current


Abbreviation for "Alternating Current"

AC coupling

Circuit that passes an AC signal while blocking a DC voltage.

AC generator

Device used to transform mechanical energy into AC electrical power.

AC load line

A graph representing all possible combinations of AC output voltage and current for an amplifier.

AC power supply

Power supply that delivers an AC voltage.

AC voltage

A voltage in which the polarity alternates.


Alternating current or direct current


Equipment that will operate on either an AC or DC power source.

acceptor atoms

Trivalent atoms that accept free electrons from pentavalent atoms.


Limitation that a measurement may vary from its true value; usually represented as a percentage of full scale, such as +1%.

across-the-line starter

Starting a motor when connected directly to the supply lines.

active component

A component that changes the amplitude of a signal between input and output.

active filter

A filter that uses an amplifier in addition to reactive components to pass or reject selected frequencies.

active power

True electrical power; power that is actually doing work.

active region

The region of BJT operation between saturation and cut-off used for linear amplification.


Analog-to-digital converter


Abbreviation for "analog to digital converter"


(symbol "Y") Measure of how easily AC will flow through a circuit. Admittance is the reciprocal of impedance and is measured in siemens.


Audio frequency


Abbreviation for "audio frequency".


Automatic frequency control


Automatic flow controller, used in controlling the flow of gasses under pressure into a vacuum system


Abbreviation for "automatic frequency control".


Automatic fine tuning


Automatic gain control


Abbreviation for "automatic gain control"


Ampere hour


Current gain

air gap

The air space between two magnetically or electrically related components; for example, the space between the armature and poles in a motor.

air-core transformer

A transformer composed of two or more coils that are wound around a non-metallic core.

alkaline cell

A primary cell that delivers more current than a carbon-zinc cell. Also known as an "alkaline manganese cell".

alligator clip

Spring clip on the end of a test lead used to make a temporary connection.


Ratio of collector current to emitter current in a bipolar junction transistor (BJT). Greek letter alpha "a" is the symbol used.

alt -


alternating current

An electrical current that constantly changes amplitude and changes in polarity at regular intervals.

alternating current

An electric current that rises to a maximum in one direction, falls back to zero and then rises to a maximum in the opposite direction and then repeats.


Device mounted on a diesel engine to charge starting batteries; sometimes used as a term for alternating current generators.


Name for an AC generator.


Amplitude modulation


Abbreviation for "amplitude modulation"


Amplitude modulation or Frequency modulation

ambient temperature

Average temperature of the air surrounding an electrical device; usually expressed in degrees Celsius (C).


Analog Multimeter


An instrument for measuring the amount of electron flow in amperes.


A meter used to measure current.




The basic unit of electrical current.


Unit of electrical current.


Production of an output larger than the corresponding input.


An electrical device producing an output signal larger than its input signal.


A circuit that increases the voltage, current, or power of a signal.


Magnitude or size of a signal voltage or current.


Information represented as continuously varying voltage or current rather than in discrete levels as opposed to digital data varying between two discrete levels.

analog device

Device that measures continuous information (voltage, current). The analog has an infinite number of possible values; its limitation is the accuracy of the measuring device. It uses a meter with a needle and scale.

analog signal

A signal having a continuous and smooth signal over a given range.

AND logic

Control circuits where all inputs must have a signal for the circuit to operate. For example, with two NO inputs in a series, both must be closed to energize the circuit.


A positive electrode of an electromagnetic device, such as a primary or secondary electric cell, toward which the negative ions are drawn.


The positive electrode or terminal of a device. The "P" material of a diode.


American national standard institute, inc.

antenna, receiving

A device that converts a radiated electromagnetic wave into an electrical wave.

antenna, transmitting

A device that converts an electrical wave into an electromagnetic wave that radiates away from the antenna.




Power gain


Automatic phase control

apparent power

That power apparently available for use in an AC circuit containing a reactive element. It is the product of effective voltage times effective current expressed in volt-amperes. It must be multiplied by the power factor to obtain true power available.

apparent power

Power attained in an AC circuit as a product of effective voltage and current which reach their peak at different times.


Discharge of electricity through a gas such as lightning discharging through the atmosphere.

arc chute

Cover around contacts to prevent arcs from reaching surrounding parts.

arc hood

Separate cover over a relay. The function is the same as an arc chute.


A winding that has an EMF induced (or produced) into it.

armature reaction

Reaction of the magnetic field coils to the magnetic field produced by current in the armature windings of a DC generator.


The rotating or moving component of a magnetic circuit.

Armstrong oscillator

An oscillator that uses an isolation transformer to achieve positive feedback from output to input.

Astable multivibrator

An oscillator that produces a square wave output from a DC voltage.


The smallest particle that an element can be broken down into and still maintain its unique identity.

atomic number

The number of positive charges or protons in the nucleus of an atom.


To reduce the amplitude of an action or signal. The opposite of amplification.


The force that tends to make two objects approach each other. Attraction exists between two unlike magnetic poles (north and south) or between two unlike static charges (plus and minus).


Relating to frequencies that can be heard by the human ear. Approximately 20 Hz. To 20 khz.



automatic controller

A motor control device that uses automatic pilot devices to turn the circuit on and off.


A transformer with a single coil. The entire length of the coil acts as a primary winding; only part of the winding functions as a secondary winding. It is used primarily as a device to reduce inrush current for motor starting.


A single winding transformer where the output is taken from taps on the winding.


Voltage gain


Automatic volume control


Abbreviation for "automatic volume control"

average value

A value of voltage or current where the area of the wave above the value equals the area of the wave below the value.

average value of AC

The average of all instantaneous values of one-half cycle of alternating current.




Aviation electronics.


American wire gauge


Abbreviation for "american wire gauge". A gauge that assigns a number value to the diameter of a wire.

AWG (American wire gauge)

A standard for wire size used by industry, replaced by the circular mil by the military.


American wire gauge


Flux density

back voltage

A term sometimes used to refer to counter EMF.

balanced bridge

Condition that occurs when a bridge circuit is adjusted to produce a zero output.

band-pass filter

A tuned circuit designed to pass a band of frequencies between a lower cut-off frequency (f1) and a higher cut-off frequency (f2). Frequencies above and below the pass band are heavily attenuated.

band-stop filter

A tuned circuit designed to stop frequencies between a lower cut-off frequency (f1) and a higher cut-off frequency (f2) of the amplifier while passing all other frequencies.


Width of the band of frequencies between the half power points.

barrier potential

The natural difference of potential that exists across a forward biased pn junction.


The region that lies betwen the emitter and collector of a bipolar junction transistor (BJT).

base biasing

A method of biasing a BJT in which the bias voltage is supplied to the base by means of a resistor.




A device for converting chemical energy into electrical energy.


A DC voltage source containing two or more cells that convert chemical enwergy to electrical energy.

battery capacity

The amount of energy available from a battery. Battery capacity is expressed in ampere-hours.


A unit of signaling speed equal to the number of signal events per second. Not necessarily the same as bits per second.


Binary coded decimal


(b) The ratio of collector current to base current in a bipolar junction transistor (BJT).


Beat frequency oscillator


A DC voltage applied to a device to control its operation.


A number system having only two symbols, 0 and 1. A base 2 number system.

bipolar junction transistor

(BJT), A three terminal device in which emitter to collector current is controlled by base current.

bistable multivibrator

A multivibrator with two stable states. An external signal is required to change the output from one state to the other. Also called a latch.


Bipolar junction transistor

bleeder current

A current drawn continously from a souce. Bleeder current is used to stabilize the output voltage of a source.

blowout coil

A coil in a relay used to stretch the arc (blow it out) when opening.

bode plot

A graph of gain versus frequency.


An individual current path in a parallel circuit.

branch current

The portion of total current flowing in one path of a parallel circuit.

breakdown voltage

Voltage at which the breakdown of a dialectric or insulator occurs.

break over voltage

Minimum voltage required to cause a diac to break down and conduct.

bridge rectifier

A circuit using four diodes to provide full wave rectification. Converts an AC voltage to a pulsating DC voltage.


A sliding contact, normally made of carbon, and riding on a commutator or slip ring to provide a mechanical contact between the rotating and stationary portions of an electrical device.


An amplifier used to isolate a load from a source.

bulk resistance

The natural resistance of a "P" type or "N" type semiconductor material.

Butterworth filter

A type of active filter characterized by a constant gain (flat response) across the midband of the circuit and a 20 db per decade roll-off rate for each pole contained in the circuit.




Abbreviation for bandwidth.

bypass capacitor

A capacitor used to provide an AC ground at some point in a circuit.


Group of eight binary digits or bits.


Centi (10-2)


Capacitance or capacitor

C (Q)



Group of two or more insulated wires.


Computer aided design


Abbreviation for "computer aided design"


To adjust the correct value of a reading by comparison to a standard.


Computer aided manufacture


The property of an electrical circuit that opposes changes in voltage.


The ability of a capacitor to store an electrical charge. The basic unit of capacitance is the Farad.

capacitive reactance

The opposition offered to the flow of alternating current by capacitance, expressed in ohms. The symbol for capacitive reactance is xc.

capacitive reactance

The opposition to current flow provided by a capacitor. Capacitive reactance is measured in ohms and varies inversly with frequency.


An electrical device capable of storing electrical energy in an electrostatic field.


An electronic component having capacitive reactance.

capacitor microphone

Microphone whose operation depends on variations in capacitance caused by varying air pressure on the movable plate of a capacitor.

capacitor start motor

An alternating current split-phase motor using a capacitor to achieve a phase shift between the start and run windings. It uses a centrifugal switch to disconnect the start winding when the motor achieves between 75 and 90 percent running speed.

carbon microphone

Microphone whose operation depends on pressure variation in carbon granules causing a change in resistance.

carbon resistor

Resistor of fixed value made by mixing carbon granules with a binder which is moulded and then baked.

carbon-film resistor

Device made by depositing a thin carbon film on a ceramic form.

cascaded amplifier

An amplifier with two or more stages arranged in a series configuration.

cascade amplifier

A high frequency amplifier made up of a common-source amplifier with a common-gate amplifier in its drain network.


The general name for any negative electrode.


The negative terminal electrode of a device. The "N" material in a junction diode.

cathode ray tube

(CRT) Vacuum tube used to display data in a visual form. Picture tube of a television or computer terminal.


Cable TV


Common base configuration


Citizen's band


Common collector


Common emitter


A single unit that transforms chemical energy into electrical energy. Batteries are made up of cells.


Single unit used to convert chemical energy into a DC electrical voltage.


Counter electromotive force

centre frequency

Frequency to which an amplifier is tuned. The frequency half way between the cut-off frequencies of a tuned circuit.

centre tap

Midway connection between the two ends of a winding.

centre tapped rectifier

Circuit that make use of a center tapped transformer and two diodes to provide full wave rectification.

centre tapped transformer

A transformer with a connection at the electrical center of a winding.

ceramic capacitor

Capacitor in which the dialectric is ceramic.


Represents electrical energy. A material having an excess of electrons is said to have a negative charge. A material having an absence of electrons is said to have a positive charge.


Quantity of electrical energy.

charge current

Current that flows to charge a capacitor or battery when voltage is applied.

charge cycle

The period of time that a capacitor in an electrical circuit is storing a charge.


Metal box or frame into which components are mounted.

chassis ground

Connection to a chassis.

chebyshev filter

A type of active filter characterized by high roll-off rates (40 db per decade per pole) and midband gain that is not constant.


A coil used in a direct current circuit to smooth out ripples or a pulsating waveform.


Inductor used to oppose the flow of alternating current.


The complete path of an electric current.


Interconnection of components to provide an electrical path between two or more components.

circuit breaker

A protective device used to open a circuit when current exceeds a maximum value. In effect a reusable fuse.

circular mil

An area equal to that of a circle with a diameter of 0.001 inch. It is used for measuring the crosssectional area of wires.


A diode circuit used to change the DC level of a waveform without distorting the waveform.

clapp oscillator

A variation of the Colpitts oscillator. An added capacitor is used to eliminate the effects of stray capacitance on the operation of the basic Colpitts oscillator.

class A amplifier

A linear amplifier biased so the active device conducts through 360 degrees of the input waveform.

class B amplifier

An amplifier with two active devices. The active components are biased so that each conducts for approximately 180 degrees of the input waveform cycle.

class C amplifier

An amplifier in which the active device conducts for less than 180 degrees of the input waveform cycle.


A diode circuit used to eliminate part of a waveform


Distortion caused by overdriving an amplifier.


A square waveform used for synchronizing and timing of several circuits.

closed circuit

Circuit having a complete path for current flow.

closed-loop gain

Gain of an amplifier when a feedback path is present.




Circular mil

coaxial cable

Transmission line in which the signal carrying conductor is covered by a dielectric and another conductor.

coefficient of coupling

The degree of coupling between two circuits.

coercive force

(H) Magnetizing force needed to reduce residual magnetism in a material to zero.


An inductive device created by looping turns of wire around a core.


The semiconductor region in a bipolar junction transistor through which a flow of charge carriers leaves the base region.

collector characteristic curve

A graph of collector voltage over collector current for a given base current.

colour code

Set of colours used to indicate value of a component.

colpitts oscillator

An oscillator with a pair of tapped capacitors in the feedback network.


Circular mil area

combination circuit

A series-parallel circuit.



common base amplifier

A BJT circuit in which the base connection is common to both input and output.

common cathode display

A multisegment light emitting diode (LED) with a single negative voltage input connection. Separate anode connections are provided for each individual segment.

common collector amplifier

A BJT circuit in which the collector connection is common to both input and output.

common drain amplifier

A FET circuit in which the drain connection is common to both input and output.

common emitter amplifier

A BJT circuit in which the emitter connection is common to both input and output.

common gate amplifier

A FET circuit in which the gate connection is common to both input and output.

common source amplifier

A FET circuit in which the source connection is common to both input and output.

common-anode display

A multisegment light emitting diode (LED) with a single positive voltage input connection. Separate cathode connections are provided for each individual segment.

common-mode rejection ratio

(CMRR) The ratio of op-amp differential gain to common-mode gain. A measure of an op-amp's ability to reject common-mode signals such as noise.

common-mode signals

Signals that appear simultaneously at two inputs of an operational amplifier (op-amp). Common mode signals are always equal in amplitude and phase.


A segmented bar section on an armature providing a place for the brushes to make contact with the armature windings.


An op-amp circuit that compares two inputs and provides a DC output indicating the polarity relationship between the inputs.

compensating windings

Windings embedded in the face of the pole pieces of a DC machine to oppose armature reaction and control arcing at the brushes.

complementary symmetry amplifier

A class B amplifier using matched complementary transistors. Does not require a phase inverter for push-pull output.

complementary transistors

Two transistors, one NPN and one PNP having near identical characteristics. N-channel and P-channel FETs can also be complementary.

complex numbers

Numbers composed of a real number part and an imaginary number part.


The maximum possible peak-to-peak output of an amplifier.

compound generator

A generator using both series and shunt windings on each pole piece.

compound motor

Direct current motor with both series and shunt windings.




The ability of a material to conduct or carry an electric current. It is the reciprocal of resistance of the material and is expressed in mhos or siemens.


Ease with which a substance transmits electricity.


A material with a large number of free electrons; a material that permits electric current to flow.

constant current circuit

Circuit used to maintain constant current to a load having resistance that changes.


Current carrying part of a switch, relay or connector.


Occurs when a complete path for current exists.

control point

The level at which a system will be maintained (such as temperature and pressure).

control voltage

Voltage level used in a control circuit to actuate coils and other devices.


A device for starting a motor in either direction of rotation or adjusting the speed of rotation.

conventional current flow

Concept of current produced by the movement of positive charges towards the negative terminal of a source.

copper loss

Power lost in transformers, generators, connecting wires and other parts of a circuit due to current flow through the resistance of copper conductors.

copper loss (I2R loss)

The power lost due to the resistance of the conductors. In transformers, the power is lost because of current flow (i) through the resistance (r) of the windings.


Any material that affords a path for magnetic flux lines in a coil.


Magnetic material within a coil used to concentrate the magnetic field.


A measure of the quantity of electricity. One coulomb equals 6.242 x 1,018 electrons.


Unit of electric charge. A negative coulomb charge consists of 6.24 1018 electrons.

Coulomb's Law

Also called the law of electric charges or the law of electrostatic attraction. Coulomb's law states charged bodies attract or repel each other with a force that is directly proportional to the product of their individual charges and inversely proportional to the square of the distance between them.

counter electromotive force

(counter e.m.f) Voltage induced into an inductor due to an alternating or pulsating current. Counter e.m.f is always in polarity opposite to that of the applied voltage. Opposing a change of current.

counter EMF (counter electromotive force)

An electromotive force (voltage) induced in a coil that opposes applied voltage; voltage induced in the coils of a load.


To electronically connect two circuits so that signal will pass from one to the other.

coupling, coefficient of

An expression of the extent to which two inductors are coupled by magnetic lines of force. This is expressed as a decimal or percentage of maximum possible coupling and represented by the letter k.

covalent bond

The way some atoms complete their valence shells by sharing valence electrons with neighbouring atoms.


Cardiopulmonary resuscitation


Central processing unit

CR cr

Junction diode


Cathode ray oscilloscope

crossover distortion

Distortion caused by both devices in a class B amplifier being cut-off at the same time.

cross-sectional area

The area of a slice of an object. When applied to electrical conductors, it is usually expressed in circular mils.


Circuit used to protect the output of a source from a short circuited load. Load current is limited to a value the source can deliver without damage.


Cathode ray tube


Abbreviation for cathode ray tube.


Natural or synthetic piezoelectric or semiconductor material with atoms arranged with some degree of geometric regularity.

crystal-controlled oscillator

Oscillator that uses a quartz crystal in its feedback path to maintain a stable output frequency.


Centrifugal switch


Total capacitance


The drift of electrons past a reference point; the passage of electrons through a conductor. It is measured in amperes.


Measured in amperes, it is the flow of electrons through a conductor. Also know as electron flow.

current amplifier

Amplifier to increase signal current.

current divider

Parallel network designed to divide the total current of a circuit

current feedback

Feedback configuration where a portion of the output current is fed back to the amplifier input.

current mirror

Term used to describe the fact that DC current through the base circuit of a class B amplifier is approximately equal to the DC collector current.

current, inrush

Current flowing into a circuit immediately upon energizing the circuit. It is normally used in conjunction with inductive loads.

current-limiting resistor

Resistor in the path of current flow to control the amount of current drawn by a device.


Condition when an active device is biased such that output current is near zero or beyond zero.

cut-off frequency

Frequency at which the power gain of an amplifier falls below 50% of maximum.


Continuous transmission


One complete positive and one complete negative alternation of a current or voltage.


When a repeating wave rises from zero to a positive maximum then back to zero and on to a negative maximum and back to zero it is said to have completed one cycle.


Deci (10-1)

D/A or D-A

Digital to analog


Abbreviation for "digital to analog converter."

damper windings

Windings embedded in the pole pieces of generators used to oppose changes in frequency or speed of the rotor. They allow generators to remain in parallel operation.


Reduction in magnitude of oscillation due to energy being dissipated as heat.

Darlington pair

An amplifier consisting of two bipolar junction transistors with their collectors connected together and the emitter of one connected to the base of the other. Circuit has an extremely high current gain and input impedance.


Direct current


Abbreviation for "direct current".

DC load line

A graph representing all possible combinations of voltage and current for a given load resistor in an amplifier.

DC offset

The change in input voltage required to produce a zero output voltage when no signal is applied to an amplifier.

DC power supply

Any source of DC power for electrical equipment.


Direct current

dead short

A short circuit having minimum resistance.

dead short

Short circuit having zero resistance.


A frequency factor of ten.


(db) a logarithmic representation of gain or loss.

degenerative feedback

Also called negative feedback. A portion of the output of an amplifier is inverted and connected back to the input. This controls the gain of the amplifier and reduces distortion and noise.

delay time

The time for collector current to reach 10% of its maximum value in a BJT switching circuit.

delta connection

Three-phase circuit where the windings are connected in the form of a closed ring or end to end. It is often used to connect windings in three-phase transformers and motors.

delta-delta connection

A transformer connection where both the input and output windings are delta-connected.

delta-wye connected

A transformer connection where the input is delta-connected and the output is wye-connected.

depletion mode

In a FET, an operating mode where reverse gate-source voltage is used to deplete the channel of free carriers. This reduces the size of the channel and increases its resistance.

depletion region

The area surrounding a pn junction that is depleted of carriers.

depletion-mode MOSFET

A MOSFET designed to operate in either depletion mode or enhancement mode.


A component or part.

Di or Di

Change in current


A two terminal bidirectional thyristor. Has a symmetrical switching mode.

dielectric constant

Property of a material that determines how much electrostatic energy can be stored per unit volume when unit voltage is applied.

dielectric strength

The maximum voltage an insulating material can withstand without breaking down.


An insulator; the insulating material between the plates of a capacitor.


Insulating material between two plates where an electrostatic field exists.

dielectric constant

The ratio of capacitance of a capacitor with a dielectric between the electrodes to the capacitance of a capacitor with air between the electrodes.

dielectric field

The space between and around charged bodies in which their influence is felt; also called electric field of force or electrostatic field.

dielectric hysteresis loss

Power loss of a capacitor due to the changes in orientation of electron orbits in the dielectric caused by rapid reversal in polarity of line voltage. The higher the frequency, the greater the loss.

dielectric leakage

Power loss of a capacitor due to leakage of current through the dielectric. It also relates to leakage resistance. The higher the leakage resistance, the lower the dielectric leakage.

differential amplifier

An amplifier in which the output is in proportion to the differences between voltages applied to its two inputs.


A circuit in which the output voltage is in proportion to the rate of change of the input voltage. A high pass RC circuit.


Tendency of conduction band electrons to wander across a pn junction to combine with valence band holes.


A class of devices in which outputs vary in discreet or distinct steps, such as pulses; test equipment that displays readings in the form of LCD or LED readouts.


Relating to devices or circuits that have outputs of only two discrete levels. Examples: 0 or 1, high or low, on or off, true or false etc.


A two terminal device that conducts in only one direction.


Dual in-line package


Abbreviation for "dual in line package."

direct coupling

Where the output of an amplifier is connected directly to the input of another amplifier or to a load. Also known as DC coupling because DC signals are not blocked.

direct current

An electric current that flows in one direction.

direct current

Current that flows in only one direction.


Release of energy stored in either a battery or a capacitor.

discrete component

Package containing only a single component as opposed to an integrated circuit containing many components in a single package.

displacement current

The current that appears to flow through a capacitor.


Release of electrical energy in the form of heat.


An undesired change in a waveform or signal.



distributed capacitance

Any capacitance other than that within a capacitor. For example, the capacitance between adjacent turns of wire in a coil.

distributed inductance

Any inductance other than that within an inductor. Example inductance in any conductor.


Digital Multimeter


A moveable magnetized area in a magnetized material. Also known as magnetic domain.

domain theory

A theory of magnetism based upon the electron-spin principle. Spinning electrons have a magnetic field. If more electrons spin in one direction than another, the atom is magnetized.

donor atoms

Pentavalent atoms that give up electrons to the conduction band in an N type semiconductor material.


The process in which a crystalline structure is altered by replacing existing atoms with those atoms from other elements. For example, germanium and silicon are base elements used in electronics. To give these base elements a more positive or negative quality, bismuth or boron atoms can be added, respectively.


The process of adding impurity atoms to intrinsic (pure) silicon or germanium to improve the conductivity of the semiconductor material.

dot convention

Standard used with transformer symbols to indicate whether the secondary voltage is in phase or out of phase with the primary voltage.

dot notation

A system used by drafters to indicate relative instantaneous polarity in AC motor and transformer windings.


Double pole double throw


Double pole, double throw


Double pole, single throw


A problem that can develop in tuned amplifiers when the frequency of the tuned circuit changes due to temperature or component aging.

dropping resistor

Resistor whose value has been chosen to drop or develop a given voltage.

drum switch

A type of motor controller using switches in the form of fingers actuated by a cam to control various contractors in a control circuit. It is usually used in reversing or braking controllers.

dry cell

An electric cell in which the electrolyte is not a liquid. In most dry cells, the electrolyte is in paste form.

dry cell

DC voltage generating chemical cell using a non-liquid (paste) electrolyte.

Dt or Dt

Change in time


Diode transistor logic

dual in-line package

Integrated circuit package having two rows of connecting pins.

dual trace oscilloscope

Oscilloscope that can simultaneously display two signals.

Dv or Dv

Change in voltage


Digital voltmeter


Relating to conditions that are changing or in motion.

dynamic braking

Braking a motor by using the motor as a generator and dissipating the generated voltage through resistors. Dynamic braking uses motor reaction to slow the motor.


Instantaneous difference in potential

E DC or Erms

Difference in potential




Emitter coupled logic


Laminated form in the shape of the letter "E", onto which inductors and transformers are wound.

eddy current

Induced circulating currents in a conducting material that are caused by a varying magnetic field.

eddy current loss

Losses caused by random current flowing in the core of a transformer. Power is lost in the form of heat.

eddy currents

Currents induced into a conducting core due to the changing magnetic field. Eddy currents produce heat which is a loss of power and lowers the efficiency of an inductor.


Electronic fuel control



effective value

Same as root mean square.


The ratio of output power to the input power; generally expressed as a percentage.


The amount of power delivered to the load of an amplifier as a percentage of the power required from the power supply.


Extremely high frequency


Extra high voltage

electric charge

Electric energy stored on the surface of a material. Also known as a static charge.

electric current

Electric energy stored on or in an object. It is the negative charge caused by an excess of electrons or the positive charge caused by a deficiency of electrons. Its symbol is q, q.

electric field

A field or force that exists in the space between two different potentials or voltages. Also known as an electrostatic field.

electric polarization

A displacement of bound charges in a dielectric when placed in an electric field.


Science states that certain particles possess a force field or charge. The charge possessed by an electron is negative while the charge possessed by a proton is positive. Electricity can be divided into two groups, static and dynamic. Static electricity deals with charges at rest and dynamic electricity deals with charges in motion.

electroacoustic transducer

Device that produces an energy transfer from electric to acoustic (sound) or from acoustic to electric. Examples include a microphone, earphones and loudspeakers.


The action of converting chemical energy into electrical energy.


The terminal at which electricity passes from one medium into another, such as in an electrical cell where the current leaves or returns to the electrolyte.


Conversion of electrical energy into light energy.


A solution of a substance that is capable of conducting electricity; may be either a liquid or a paste.


Electrically conducting liquid (wet) or paste (dry)

electrolytic capacitor

A capacitor having an electrolyte between the two plates. A thin layer of oxide is deposited on only the positive plate. The oxide acts as the dielectric for the capacitor. Electrolytic capacitors are polarized and so must be connected in correct polarity to prevent breakdown.


An electrically excited magnet capable of exerting mechanical force or performing mechanical work.


A coil of wire usually wound on a soft iron or steel core. When current is passed through the coil a magnetic field is generated. The core provides an easy path for the magnetic lines of force. This concentrates the field in the core.


Describes the relationship between electricity and magnetism; having both magnetic and electrical properties.

electromagnetic communication

Use of an electromagnetic wave to pass information between two points. Also called wireless communication.

electromagnetic induction

The production of a voltage in a coil due to a change in the number of magnetic lines of force (flux linkages) passing through the coil.

electromagnetic induction

Voltage produced in a coil due to relative motion between the coil and magnetic lines of force.

electromagnetic spectrum

List or diagram showing the range of electromagnetic radiation.

electromagnetic wave

Wave that consists of both electric and magnetic variation.


The generation of a magnetic field around a current-carrying conductor.


Relates to the magnetic field generated around a conductor when current is passed through it.

electromechanical transducer

Device that transforms electrical energy into mechanical energy (electric motor) or mechanical energy into electrical energy (generator).

electromotive force

(e.m.f) Force that causes the motion of electrons due to potential difference between two points. (voltage)


The elementary negative charge that revolves around the nucleus of an atom.


Smallest sub atomic particle of negative charge that orbits the nucleus of an atom.

electron flow

Electrical current produced by the movement of free electrons towards a positive terminal.

electron shell

A group of electrons that have a common energy level that forms part of the outer structure (shell) of an atom.

Electronic warfare



Pertaining to electricity at rest, such as charges on an object (static electricity).


Related to static electric charge.

electrostatic field

The field of influence between two charged bodies.

electrostatic field

Force field produced by static electrical charges.


A substance in chemistry that cannot be divided into simpler substances by any means normally available.


Extremely low frequency


Electromotive force

EMF (electromotive force)

The force that causes electricity to flow between two points with different electrical charges; or when there is a difference in potential between the two points, the unit of measurement in volts.


Electromotive force


Electromagnetic interference


The semiconductor region from which charge carriers are injected into the base of a bipolar junction transistor.

emitter feedback

Coupling from the emitter output to the base input of a bipolar junction transistor.

emitter follower

A common collector amplifier. Has a high current gain, high input impedance and low output impedance.


Being electrically connected to a voltage source so the device is activated.


The ability or capacity to do work.


Capacity to do work.

engineering notation

A floating point system in which numbers are expressed as products consisting of a number greater than one multiplied by an appropriate power of ten that is some multiple of three.

enhancement-mode MOSFET

A field effect transistor in which there are no charge carriers in the channel when the gate source voltage is zero.

equivalent resistance

A resistance that represents the total ohmic values of a circuit component or group of circuit components. It is usually drawn as a single resistor when simplifying complex circuits.

equivalent resistance

Total resistance of all the individual resistances in a circuit.


Electronic warfare




Creating a magnetic field; passing current through a conductor to create an electromagnetic field.

excitation current

The current that produces the magnetic field in a generator; the current that flows in the primary winding of a transformer, which produces a magnetic flux field. It is also called magnetizing current.



fall time

Time it takes the falling edge of a pulse to go from 90% of peak voltage to 10% of peak voltage.


The basic unit of capacitance. A capacitor has a capacitance of 1 farad when a voltage change of 1 volt per second across it produces a current of 1 ampere.


The basic unit of capacitance.


A portion of the output signal of an amplifier which is connected back to the input of the same amplifier.

feedback amplifier

An amplifier with an external signal path from its output back to its input.


A powdered, compressed and sintered magnetic material having high resistivity. The high resistance makes eddy current losses low at high frequencies.

ferrite bead

Ferrite composition in the form of a bead. Running a wire through the bead increases the inductance of the wire.

ferrite-core inductor

An inductor wound on a ferrite core.


Compound composed of iron oxide, a metallic oxide and ceramic. The metal oxides include zinc, nickel, cobalt or iron.

ferromagnetic material

A highly magnetic material, such as iron, cobalt, nickel, or alloys.