Glossary

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a b c d e f g h i j k l m n o p q r s t u v w x y z

 

alternating current current that reverses its direction of flow at periodic intervals

 

ambient air temperature the temperature of the surrounding air

American Wire Gauge (AWG) an English standard for measuring the diameter of wire

  ammeter a device for measuring current flow

ammeter shunt a device that allows an ammeter to measure large amounts of current; the shunt is connected in series with the load and the ammeter is connected in parallel with the shunt

 

amp a measure of electric current defined as one coulomb per second

  ampacity the amount of current that a wire can carry
  amplitude the maximum height reached by a waveform
 

analog meters meters that employ a moving pointer to indicate a value

 

angle theta (_u) the phase angle difference between

voltage and current in a circuit containing a reactive component such as an inductor or capacitor

 

apparent power (VA) the value found by multiplying the applied voltage by the total current of an AC circuit. Apparent power is measured in volt-amps (VA) and should not be confused with true power, measured in watts.

 

apparent power volt amps (VA) the product of the total applied voltage and the total current flow in an AC circuit

 

appear to flow the charging and discharging of a capacitor will cause current to appear to flow through a capacitor when it is connected to an AC circuit

 

artificial respiration a method of providing oxygen to a

person unable to breath on his or her own

 

atom the smallest part of an element, atoms are composed of three primary sub atomic particles; the proton, the neutron, and the electron

 

atomic number the number of protons located in the nucleus of an atom

 

attraction generally the force that exists between objects that contain opposite charges

 

autotransformer a transformer that uses only one winding for both the primary and secondary

 

average the value of voltage when an AC sine wave voltage is changed to DC

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bidirectional a device that can conduct current in either direction, or current that flows in two directions

 

British thermal unit (BTU) the amount of heat necessary to change the temperature of one pound of water one degree Fahrenheit

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capacitive reactance (Xc) the current-limiting effect of a

capacitor

 

carbon film resistor a resistor made by coating a nonconducting material with a film of carbon

 

centrifugal force the force that causes a spinning object to pull away from its axis point

 

centrifugal switch a switch used to disconnect the start windings in a split-phase motor after the motor has accelerated to approximately 75% of rated speed

 

chassis ground a conductor connected to the metal case of a piece of equipment for the purpose of placing the case at ground potential

 

circuit branch (a) in the case of parallel circuits, a circuit derived from a main set of circuit conductors that supply power to multiple other circuits; (b) normally the circuit that supplies power to electrical equipment from the last protective device, such as a fuse or circuit breaker

 

circuit breakers devices that disconnect power to a circuit in the event of an excessive amount of current

 

circular mil an English measure for determining the crosssectional area of round wire; circular mils is the diameter in mils (1 mil 5 0.001 in.) squared

 

clamp-on ammeter an ammeter with a movable jaw that can be clamped around a conductor to measure current flow

color code a method of marking the resistance and tolerance of a resistor with bands of color

 

combination circuit a circuit that contains both series

and parallel circuits

 

compensating winding a winding used in universal motors

to counteract the inductive reactance in the armature windings

 

complete path an electric circuit that exists from the

more negative to the more positive voltage

composition carbon resistor a resistor that is made by combining carbon with a resin material

conductive compensation accomplished by connecting the compensating winding of a universal motor in series with the field winding

  conductors materials that conduct electricity easily
  confined space a space that has limited entrances or exits
 

control transformer a common type of transformer used in motor control circuits to reduce the rated line voltage to the amount needed to operate the control components

conventional current flow theory an older theory stating that electric current flows from the more positive source to the more negative source

 

correction factor a decimal fraction employed to determine the amount of current a conductor is permitted to carry over a range of ambient temperature

 

coulomb a quantity measure of electrons that equals

electrons

  CPR an acronym for cardiopulmonary resuscitation
 

current adds one of the three rules used to solve values of voltage, current, resistance, and power in a parallel circuit

 

current divider formula a formula used to calculate the amount of current flow in any branch when the total circuit current and resistance are known

 

current flow through the inductor (IL) the amount of current flowing through the inductor

 

current lags voltage the relationship of current and voltage in a pure inductive circuit

 

current transformer a transformer used to measure large values of AC current

 

cycle one cycle is completed when an AC voltage completes 360 degrees

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d’Arsonval movement a galvanometer that employs a moving coil suspended inside a permanent magnet to move a pointer

 

damp location a location that is covered and not likely to be saturated by water

 

de-energized circuit a circuit that has been disconnected from the power supply

  dielectric the insulation between the plates of a capacitor
 

dielectric stress the stretching of the molecular structure of the dielectric

 

direct current (DC) current that flows in only one direction

 

disconnect to turn off or remove power from a circuit

 

distribution transformer a transformer that is generally used to lower the power company line voltage to the value needed for houses or industrial plants

 

dry location a location that is not normally subject to

dampness or wetness

 

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earth ground point at which a metal rod is driven into the ground to provide a low-resistance path to the earth

 

eddy current electric currents induced in metal; generally core material of motors and transformers

 

egress an entrance or exit into a structure

 

electrolytic a type of capacitor that is polarity sensitive

 

electromotive force (EMF) the force known as voltage that pushes the electrons through an electric circuit

 

electron orbit the space in which an electron circles thenucleus of an atom

 

electron theory the theory stating that electricity flows

from the more negative power source to the more positive power source

 

electron a sub atomic particle that orbits the nucleus of an atom and contains a negative charge

 

electrostatic charge the charge of a capacitor produced by the stressing of the molecules in the dielectric

 

element a material, the smallest part of which would be anatom

 

energized circuit a circuit connected to the power supply; a voltage or potential exists between conductors

 

excitation current the amount of current that flows in the primary winding of a transformer when no load is connected to the secondary

 

exponential the rate at which a capacitor charges and discharges

 

exponential curve a rate at which current increases or decreases in an inductor

 

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farad the unit measure of capacitance

 

fibrillation a condition in which the heart starts to quiver

and stops its pumping action

 

fire retardant clothing clothing made from a specially

treated material that resists ignition; many industries require electricians to wear this type of clothing

 

flux leakage the amount of magnetic flux lines that radiate into the air

 

frequency the number of complete cycles that occur in one second

 

frequency the number of times per second that the current changes direction in an alternating current circuit

 

fuses devices that disconnect power to a circuit in the

event of an excessive amount of current

 

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galvanometers very sensitive meters that require only a few microamperes of current to operate

 

general voltage divider formula a formula employed to determine the value of resistance needed to produce a certain voltage drop

 

ground point point at which a circuit or device is

grounded

 

grounding conductor generally the bare or green wireused to establish a low resistance path to ground

 

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henry the standard measure of inductance

 

hertz a measure of frequency

 

HIPOT an instrument that develops a high potential or high voltage for testing the dielectric of a capacitor

Holtz motor a type of single-phase synchronous
motor
that operates at a speed of 1200 RPM

 

horseplay playing practical jokes or exhibiting adolescent behavior in an inappropriate place

 

horsepower a common measure of power in which the base is established at 550 pound feet per second; in electrical quantities, 746 watts equals one horsepower

 

hysteresis loss the amount of power loss in the form of

heat caused by molecular friction

 

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idiot proofing designing a piece of equipment so it cannotbe misused by an experienced person

 

impedance the total current limiting effect in an electric

circuit; impedance is measured in ohms.

 

impedance (Z) the total current-limiting effect in an AC

circuit

 

in phase a condition that occurs when the voltage and current reach peak values and zero crossing at the same time

 

induced voltage voltage that is supplied to a conductor

by cutting lines of magnetic flux

 

inductance (L) the property of an electric circuit whereby voltage is produced by cutting magnetic flux lines

inductive compensation accomplished by shorting the compensating winding leads together and permitting induced voltage to supply current to the winding

 

inductive reactance (XL) the current-limiting effect of a pure inductor

 

inrush current the amount of current flow that occurs

when power is first applied to a transformer

 

insulation the plastic or rubber coating around the conductor

 

insulators materials that hinder the flow of electricity

isolation transformers transformers that have their primary and secondary windings electrically separated from each other

 

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joule a metric measure of power similar to the English measure watt

 

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laminated the process of stacking thin sheets of metal together to form the core material for a transformer

 

leakage current the amount of current that flows through the dielectric of a capacitor

 

Lenz’s law an electrical law stated by a scientist named

Lenz that says, basically, that an induced voltage will always oppose the force that induces it

 

linear wave a waveform that increases in the same proportion as the angle of rotation

 

load the amount of power a circuit is supplying to a device

 

lock out and tag out a procedure to prevent a circuit

from being energized accidentally

 

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magnetic induction using magnetic field to induce a voltage into a conductive material, generally wire

 

matter any material composed of atoms

 

maximum operating temperature the maximum temperature in an area where the wire is to be used

 

MEGGER® a device used to measure the insulation resistance; meggers measure resistance in millions of ohms

metal film resistor a resistor made by coating a nonconducting material with a film of metal

 

metal glaze resistor a resistor made by combining glass and metal

 

metal oxide varistor (MOV) an electronic device that exhibits a rapid change of resistance with a change of temperature

 

meter an instrument used to test for some electrical quantity such as voltage, current, or resistance

 

mil foot an English standard of measure for wire; a mil foot is a piece of wire one thousandth of an inch in diameter and one foot long

 

milliamperes one milliampere equals 1/1000 of an amp

(0.001)

 

molecules a combination of atoms that form the smallest part of a compound

 

MSDS an acronym for material safety data sheets

 

multirange voltmeters voltmeters that employ more than one full range value

 

multispeed motors motors designed to operate at more than one full load speed

multiturn variable resistors resistors constructed so

that their ohmic value can be adjusted by turning a shaft

from three to ten turns

 

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National Electrical Code a national standard for installation of electrical apparatus and equipment published by the National Fire Protection Association

 

negative a charge formed by an excess of electrons

 

neutral conductor a conductor is generally grounded and is a common connection to other parts of a circuit

 

neutral conductor the part of an electric circuit that is

generally grounded

 

neutral plane the point at which no voltage is induced in the armature winding

 

neutron one of the principal parts of an atom. The neutron has no charge and is part of the nucleus.

 

node a point of connection

 

nonpolarized capacitors capacitors that are not sensitive to voltage polarity

 

nucleus the center or core of an object

 

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ohm (V) the unit of measure used to describe the resistance to the flow of electric current

 

Ohm’s law a set of mathematical formulas developed by

the German scientist Georg S. Ohm

 

ohmmeter a meter used to measure values of resistance one of three formulas used to determine the total resistance of resistors connected in parallel

 

oscillators devices used to convert direct current into alternating current

 

OSHA an acronym for Occupational Safety and Health Administration

 

out of phase a condition that occurs between the voltage and current in a capacitive circuit

 

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parallel block a section of a combination circuit composed of parallel resistors

 

parallel circuits circuits with more than one path for current flow

  parallel conductors conductors connected in parallel with each other for the purpose of carrying more electric current
 

parallelogram method a method of obtaining values of voltage, current, impedance, and power with vectors

 

peak the maximum value obtained by a waverform

 

plates thin, flat metal used in the construction of a capacitor

 

polarized capacitors capacitors that are sensitive to voltage polarity

 

positive a charge formed by a lack of electrons

 

pot slang for potentiometer

 

potentiometer a variable resistor employed in such a

manner that it can provide a variable voltage

 

power the ability to do work; in an electric circuit, it is

generally measured in watts

 

power factor (PF) the ratio of true power to apparent

power

 

primary winding the winding of a transformer to which

power is connected

 

product over sum formula one of three formulas used to determine the total resistance of resistors connected in parallel

 

proton a sub-atomic particle located in the nucleus of an atom; the proton has a positive charge

 

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quadrature power often referred to as VARs, reactive power, or wattless power

 

quality (Q) the ratio of capacitive reactance to resistance in a capacitor

 

quality (Q) the ratio of inductive reactance as compared

with resistance

 

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RC time constant the time required for a capacitor to charge or discharge when it is connected in series with a resistance

 

reactance the property of a circuit that limits current by

means other than resistance

 

reactive power (VARs) volt amps reactive; often called wattless power, VARs is the product of the current and voltage in a pure reactive load

 

reactive power (VARs) Volt-Amps Reactive; often referred to as wattless power

 

reciprocal formula one of three formulas used to determine the total resistance of resistors connected in parallel

 

reduce a method employed to simplify parallel or series

connected components into a single resistor

 

repulsion generally the force that exists between two objects that contain like electrical charges

 

resistance the element of an electric circuit that can limit the flow of current by producing heat

 

resistance adds one of the major rules concerning series circuits

 

resistive loads loads that employ resistance to limit circuit current

 

rheostat a variable resistor that contains only two terminals

 

ripple the turning on and off effect that occurs when alternating current is converted into direct current

 

R-L time constant the amount of time required for current to increase or decrease in value

 

root mean square (RMS) the amount of AC voltage that will produce the same heating effect as a like amount of DC voltage

 

run winding one of the windings in a split-phase motor

 

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scaffold a platform for working in high places, generally designed so it can be taken apart and transported to a different job site or area

 

secondary winding the winding of a transformer to which the load is connected

 

series circuit a circuit that contains only one path for current flow

 

series resistance resistance connected in series with

other circuit components

shaded-pole induction motor a single-phase motor that produces a rotating magnetic field by shading one side of each pole piece; shading is accomplished by placing a loop of large copper wire around one side of the pole piece

 

shading coil the loop of large wire used to form a shaded pole

 

short circuit a circuit that contains almost no resistance

to limit the flow of current

 

sine wave a waveform produced by any rotating machine. The voltage at any point on the waveform can be determined by multiplying the peak value by the sine of the angle of rotation

 

skin effect the effect that causes electrons to move toward the outside of a conductor in an alternating current circuit

 

split-phase motor a type of single-phase motor that

splits the current flow through two separate windings to produce a rotating magnetic field

 

start winding one of the windings used in a split-phase

motor

 

step-down transformer a transformer that produces a lower secondary voltage than primary voltage

 

step-up transformer a transformer that produces a higher secondary voltage than primary voltage

 

strength of magnetic field the number of magnetic flux lines per square inch or flux density of a magnetic field

 

surface area one of the factors that determines the

amount of capacitance a capacitor will have

 

synchronous motors motors that operate at a constant speed from no load to full load

 

synchronous speed the speed of the rotating magnetic field of an AC induction motor

 

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tape wound core a type of transformer core made by winding a long continuous metal sheet in a circular or

rounded-rectangle shape

 

tolerance the range over which a resistor is considered to be within its marked value

 

toroid core a transformer core that is in a toroid shape,

which is generally round with a hole in the center similar to a donut

 

total current (IT) the total current flow in an electric circuit

 

total current (IT) the total current flow in an electric circuit; in an RL parallel circuit it is determined by vector addition

of the resistive current and inductive current

 

total impedance the total current-limiting effect in an AC circuit

 

total impedance the total current-limiting effect in an AC circuit

 

trace the current path a method used to determine if

components are connected in series or parallel

 

transformer an electrical machine used to change values of voltage, current, and impedance

 

triangle wave a linear waveform in which the voltage is proportional to the peak value and percent of angle of rotation

 

true power the amount of electrical energy that is converted into some other form of energy such as thermal or kinetic; also known as watts

 

turns of wire the number of turns of wire on a coil

 

turns ratio the ratio of the number of turns of wire in the primary winding compared with the number of turns in the secondary winding

 

two phase a power system that produces two separate

phase voltages 90° apart

 

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unidirectional something that moves in only one direction

 

universal motor a type of single-phase motor that can operate on either direct or alternating current

 

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valence electrons electrons located in the outermost orbit or shell of an atom

variable capacitors capacitors that can be adjusted for

different values of capacitance her12945_glo.qxd 9/13/02 7:32 AM Page 281

variable resistor a resistor whose resistance value can be changed

 

vector addition the process of using vectors to add like

electrical values

 

vector a line that indicates both magnitude and direction

 

volt a measure of EMF often described as electrical pressure

 

voltage divider a circuit generally constructed of series

connected resistors to provide different amounts of voltage

 

voltage divider a circuit used to provide different values of voltage

 

voltage drop the amount of voltage employed to push current through the resistance of the wire

 

voltage drop the amount of voltage existing across any

component that limits the flow of current; voltage drop indicates the amount of voltage necessary to push current

through a limiting element

 

voltage polarity the polarity, positive or negative, of the voltage at a certain point in a circuit

 

voltage rating the amount of voltage that can be safely

applied to a capacitor without damaging the dielectric

 

voltage spike a large amount of voltage that exists for a very short period of time

 

voltmeter a meter used to measure voltage

 

volts-per-turn ratio a method of determining voltage values in a transformer by dividing the number of turns of wire in the primary winding by the voltage applied voltage

 

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Warren motor a type of single-phase synchronous motor that operates at a speed of 3600 RPM

 

watt a power measurement that describes the amount of electrical energy converted to some other form

 

wattless power VARs; computed by using values that pertain only to reactive components such as inductors or capacitors

 

watts a measure of electric power

 

watts the true power in a circuit; indicates the amount of electrical energy converted to some other form

 

weber a measure of magnetism equal to 100,000,000 lines of magnetic flux

 

wet location areas that are subject to saturation by water; some of these areas include direct burial in the earth, underground conduit installations, or installation in masonry or concrete slabs

 

wire wound resistor a resistor made with a high-resistance metal wire such as Nichrome

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