# Power Factor

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Related to power factors: Apparent power

## power factor

[′pau̇·ər ‚fak·tər] (electricity)

The ratio of the average (or active) power to the apparent power (root-mean-square voltage times rms current) of an alternating-current circuit. Abbreviated pf. Also known as phase factor.

## Power Factor

(cos ɸ), the ratio of the average power of alternating current to the product of the effective values of voltage and current. The maximum value of the power factor is 1. For a sinusoidal alternating current, the power factor is equal to the angle of the phase shift between the sine curves of voltage and current and is determined by the circuit parameters: cos ɸ = *r/Z*, where ɸ is the phase shift angle, *r* is the effective resistance of the circuit, and Z is the total impedance. The power factor may have a value different from 1 even in circuits containing only resistances, if the circuits contain any nonlinear sections. In this case the power factor is decreased because of the distorted shape of voltage and current curves.

## power factor

In an alternating current, the ratio of the average power (expressed in watts) to the apparent power (expressed in volt-amperes).