**Electrical resistance** (measured in Ohms) is a measure of how much current will flow through a circuit for a given voltage. It is the reciprocal of **conductance**. A related property is electrical resistivity, *ρ* which is property inherent to the material, given by

- $ \rho = R \frac{A}{L} $

For DC circuits, resistance is related to voltage and current by Ohm's law,

- $ V = IR $

For AC circuits, it is the real part of impedance.