# impedance

## Definitions

### Aviation

### Computing

- noun a measurement of the effect an electrical circuit or
__cable__ has on signal current magnitude and __phase__ when a steady voltage is applied.

### Construction

- Measured in ohms, the total opposition or resistance to the flow of current when voltage is applied to an alternating current electric circuit.

### Electronics

- Its
__symbol__ is *Z.* The total __opposition__ a circuit or device offers to the flow of AC. It is a __complex quantity__, whose real number __component__ is resistance, and whose __imaginary number__ component is reactance. Its __formula__ is: *Z* = *R +jX*, in which *Z* is the impedance, *R* is the resistance, *X* is the reactance, and *j* is the __square__ root of -1. That is, *j*^{2} = -1. *Z* is expressed in ohms. Also called electrical impedance.

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