Editing Electrical impedance (section)

===Resistor===
[[File:VI phase.svg|thumb|right|250px|The phase angles in the equations for the impedance of capacitors and inductors indicate that the voltage across a capacitor ''lags'' the current through it by a phase of <math>\pi/2</math>, while the voltage across an inductor ''leads'' the current through it by <math>\pi/2</math>. The identical voltage and current amplitudes indicate that the magnitude of the impedance is equal to one.]]

The impedance of an ideal [[resistor]] is purely [[Real number|real]] and is called ''resistive impedance'':

:<math>\ Z_R = R</math>

In this case, the voltage and current waveforms are proportional and in phase.