Impedance
n.
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 R 2 + X 2 , 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.
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