Impedance

Impedance is a property of electrical circuits that "impedes" current from flowing. Fundamentally, there are two types of impedance: Resistance and Reactance.

The magnitude of impedance (represented by $$Z\,$$) of a circuit or component can be computed by taking the sum of the squares of the resistance (represented by $$R\,$$) and reactance (represented by $$X\,$$).

$$Z = \sqrt{R^2 + X^2}\,$$

However, it is more useful to represent impedance as a complex number and use it in phasor analysis.

Impedance can be used in the normal Ohm's Law equation:

$$V = IZ\,$$

where V is voltage and I is current. For working with alternating current, this is more correct than the usual direct current equation $$V = IR\,$$.