# 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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