impedance
An impedance(Z) is an impedance that results from the geometric addition of a real, ohmic resistance (R), and an imaginary reactance (X). An impedance can be a series or parallel connection of a capacitor or an inductor with an ohmic resistor.
In such a circuit, when an AC voltage is applied, there are frequency-dependent phase shifts between the current and the applied voltage. This results in a complex AC resistance consisting of an ohmic resistance and an imaginary resistance, the reactance. In the standardized, vectorial representation of ohmic resistance and reactance, the ohmic resistances are represented in the horizontal, the reactances in the vertical: the inductive reactances in positive, the capacitive resistances in negative direction. The geometric addition of active resistance and reactance results in the apparent resistance.