# Electrical Impedance

(redirected from Impedence)

## 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

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Impedance, Electrical

a quantity characterizing the opposition presented by a circuit to an alternating current. Often called simply impedance, it is measured in ohms. In the case of a sinusoidal alternating current, the impedance is expressed by the ratio of the amplitude of the voltage applied to the circuit terminals and the amplitude of the current throught the circuit; here, the impedance is equal to , where r is the resistance and x is the reactance. In the case of a nonsinusoidal alternating current, the impedance is determined separately for each kth har monic component: .

## 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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
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Accuracy of bioelectrical impedence consumer devices for measurement of body composition in comparison to whole body magnetic resonance imaging and dual x-ray absorptiometry.
The DXCCII presented in [15], even though contains a buffered output, requires an additional current source to obtain a low output impedence terminal, while, in this work, no additional current source is required.
For the transmission performance enhancement to the transition, the tapered structure with length [L.sub.1] in the region from the cross-sectional CC' to the DD' is employed, and this smooth transition ensures the field and impedence matching between SIW 180[degrees] PS output port and SICL in the broad bandwidth.

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