Electrical Definitions


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Electrical Definitions

Letter - P


A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.


Peak Value

The highest or maximum value of an alternation of alternating current or voltage. This peak value occurs twice during each cycle.


Peak-to-Peak Value

The maximum voltage change occuring during one cycle of alternating voltage or current. The total amount of voltage between the positive peak and the negative peak of one cycle or twice the peak value.



The time required for the current to pass through one cycle.



The factional part of the period of a sinusoidal wave, usually expressed in electrical degrees and referenced to the origin.


Phase Angle

(See "Phase Difference")


Phase Difference

The difference in phase between two sinusoidal waves having the same period, usually expressed in electrical degrees. The voltage wave if generally taken as the reference, so in an inductive circuit the current lags the voltage, and in a capacitive circuit the current leads the voltage. Sometimes called the phase angle.



A compartment or chamber to which one or more air ducts are connected and that forms part of the air distribution system.



A general term applied to any system of more than a single phase. This term is ordinarily applied to symmetrical systems.


Potential Transformer

A transformer designed for shunt or parallel connection in its primary circuit, with the ratio of transformation appearing as a ratio of potential differences.



Rate of work, equals work divided by time.


Power Factor

Watts divided by voltamps (VA), KW divided by KVA. Power factor: leading and lagging of voltage versus current caused by inductive or capacitive loads, and 2) harmonic power factor: from nonlinear current.


Power Outlet

An enclosed assembly that may include receptacles, circuit breakers, fuseholders, fused switches, buses, and watt-hour meter mounting means; intended to supply and control power to mobile homes, recreational vehicles, park trailers, or boats or to serve as a means for distributing power required to operate mobile or temporarily installed equipment.


Premises Wiring (System)

That interior and exterior wiring, including power, lighting, control, and signal circuit wiring together with all their associated hardware, fittings, and wiring devices, both permanently and temporarily installed, that extends from the service point or source of power, such as a battery, a solar photovoltaic system, or a generator, transformer, or converter windings, to the outlet(s). Such wiring does not include wiring internal to appliances, luminaires (fixtures), motors, controllers, motor control centers, and similar equipment.



The windings of a transformer which receive energy from the supply circuit.


Pulsating Current.

Direct current which changes regularly in magnitude.