Impedance

English Meaning

The apparent resistance in an electric circuit to the flow of an alternating current, analogous to the actual electrical resistance to a direct current, being the ratio of electromotive force to the current. It is equal to R² + X², where R = ohmic resistance, X = reactance. For an inductive circuit, X = 2πfL, where f = frequency and L = self-inductance; for a circuit with capacity X = 1 ÷ 2πfC, where C = capacity.

1. A measure of the total opposition to current flow in an alternating current circuit, made up of two components, ohmic resistance and reactance, and usually represented in complex notation as Z = R + iX, where R is the ohmic resistance and X is the reactance.
2. An analogous measure of resistance to an alternating effect, as the resistance to vibration of the medium in sound transmission.