The measure of energy given to the charge flowing in a circuit. The greater the voltage, the greater the force or “pressure” that drives the charge through the circuit. Example – you could say that: Amps measure how much water comes out of a hose. Volts measure how hard the water comes out of a hose. Voltage, also called electromotive force, is a quantitative expression of the potential difference in charge between two points in an electrical field.