# Impedance: Everything You Need to Know

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 $V = IR\,$.