Electrical Resistance of a circuit element is a property of the type of material and its size (length and diameter). The units of electrical resistance (R) is Ohms. The larger the surface area of a wire, the smaller the resistance, and the longer the the length of the wire, the greater the resistance.

The resistance of a metal also increases with an increase in temperature.
The quantities of resistance, potential difference and current are related to each other by a formula known as **Ohm's Law**:

I = V/R or V = IR

where I is the current and V is the potential difference or voltage.

Different materials have different reactivities. Superconductors have a resistivity of 0 at low temperatures.