(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.