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Glossary
Electrical Theory & Applications for HVACR
O
ohm
unit of electrical resistance; symbol is Ω
ohmmeter
instrument used to measure resistance
Ohm’s Law
voltage equals current Ɵmes resistance
open circuit
an interrupted electrical circuit that does not provide a complete path for current flow
oscillator
a device that changes DC voltage into AC voltage
oscilloscope
a cathode ray tube (CRT) that displays voltage (verƟcal scale) and Ɵme (horizontal scale)
out‐of‐phase
the condiƟon resulƟng when two components do not reach their posiƟve and negaƟve peaks at the
same Ɵme
overcurrent
a condiƟon in an electrical circuit when the normal current is exceeded; can be caused by an overload
or a short circuit
P
pos
abbreviaƟon for posiƟve
panel box
electrical juncƟon box that contains fuses or breakers
parallel circuit
a circuit that feeds idenƟcal voltage to all branch circuits or components, with amperage dividing
among the components
peak load
the maximum load carried by a unit during a designated period of Ɵme
peak‐to‐peak voltage
the measurement of voltage from the posiƟve peak to the negaƟve peak of an AC sine wave