RG59 coaxial cable spool 200m

The impedance (Z) is a measure of opposition that a circuit to a current when a voltage is applied. The impedance extends the concept of resistance circuits alternating current (AC), and has both magnitude and phase, unlike resistance, which has only magnitude. When a circuit is powered with direct current (DC), there is no distinction between the impedance and resistance; the latter can be thought csa impedance with zero phase angle.