13 Facts About Electrical impedance

In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit.

Notion of impedance is useful for performing AC analysis of electrical networks, because it allows relating sinusoidal voltages and currents by a simple linear law.

In multiple port networks, the two-terminal definition of Electrical impedance is inadequate, but the complex voltages at the ports and the currents flowing through them are still linearly related by the Electrical impedance matrix.

Reciprocal of Electrical impedance is admittance, whose SI unit is the siemens, formerly called mho.

Where the real part of Electrical impedance is the resistance and the imaginary part is the reactance.

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Just as Electrical impedance extends Ohm's law to cover AC circuits, other results from DC circuit analysis, such as voltage division, current division, Thevenin's theorem and Norton's theorem, can be extended to AC circuits by replacing resistance with Electrical impedance.

The concept of Electrical impedance can be extended to a circuit energised with any arbitrary signal by using complex frequency instead of j?.

For steady-state AC, the polar form of the complex Electrical impedance relates the amplitude and phase of the voltage and current.

Capacitor has a purely reactive Electrical impedance that is inversely proportional to the signal frequency.

Equivalent Electrical impedance can be calculated in terms of the equivalent series resistance and reactance.

Measurement of the Electrical impedance of devices and transmission lines is a practical problem in radio technology and other fields.

The measurement of Electrical impedance requires the measurement of the magnitude of voltage and current, and the phase difference between them.

Impedance is often measured by "bridge" methods, similar to the direct-current Wheatstone bridge; a calibrated reference Electrical impedance is adjusted to balance off the effect of the Electrical impedance of the device under test.