electrical impedance

electrical impedance

Opposition that a circuit presents to electric current. It includes both resistance and reactance. Resistance arises from collisions of the current-carrying charged particles with the internal structure of the conductor. Reactance is an additional opposition to the movement of electric charge that arises from the changing electric and magnetic fields in circuits carrying alternating current. Impedance in circuits carrying steady direct currents is simply resistance. The magnitude of the impedance Z of a circuit is equal to the maximum value of the potential difference, or voltage V, across the circuit, divided by the maximum value of the current I through the circuit, or simply Z = V/I. The unit of impedance is the ohm.

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electrical impedance [i′lek·trə·kəl im′pēd·əns]

Also known as impedance.

(electricity)

The total opposition that a circuit presents to an alternating current, equal to the complex ratio of the voltage to the current in complex notation. Also known as complex impedance.

The ratio of the maximum voltage in an alternating-current circuit to the maximum current; equal to the magnitude of the quantity in the first definition.

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Electrical impedance

The measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current (ac) circuit.

A generalized ac circuit may be composed of the interconnection of various types of circuit elements. The impedance of the circuit is given by Z = V/I, where Z is a complex number given by Z = R + jX. R, the real part of the impedance, is the resistance of the circuit, and X, the imaginary part of the impedance, is the reactance of the circuit. The units of impedance are ohms. See Electrical resistance, Reactance