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Glossary
Electrical Theory & Applications for HVACR
diac
a semiconductor most oŌen used as a voltage‐sensiƟve switching device
dielectric
an insulaƟng material separaƟng the conducƟng surfaces of a capacitor
digital voltmeter
a voltmeter that uses direct numerical display as opposed to a meter movement
diode
a solid‐state device that allows current to flow only in one direcƟon; will recƟfy alternaƟng current to
direct current
direct current (DC)
current that flows in only one direcƟon in a circuit
distribuƟon center
an electrical panel that supplies electricity to several places in a structure
doping
adding an impurity to a semiconductor to produce a desired change in electrical properƟes
double‐pole breaker
a circuit breaker used to disconnect both hot wires with a single on‐off acƟon
double‐pole double‐throw switch
a switch with two poles and two contacts for each pole; two contacts are always open and the other
two always closed
double‐pole single‐throw switch
a switch arranged so that both switches are either open or closed
duty cycle
the relaƟonship between operaƟng Ɵme and off Ɵme; duty cycle of a motor is usually referred to as
conƟnuous or intermiƩent
E
E
symbol for voltage (electromoƟve force)
earth
term for zero reference ground
eddy current
induced current flowing in a magneƟc core created by a varying magneƟc field