In thehydraulic analogy sometimes used to explain electric circuits by comparing them to water-filled pipes,voltage is like water pressure - it determines how fast the electrons will travel through the circuit. Current (in amperes), in the same analogy, is a measure of thevolume of water that flows past a given point, the rate of which is determined by the voltage, and the total output measured in watts. The equation that brings all three components together is: volts × amperes = watts
In 1800, as the result of a professional disagreement over the galvanic response advocated byLuigi Galvani, Alessandro Volta developed the so-calledVoltaic pile, a forerunner of thebattery, which produced a steady electriccurrent. Volta had determined that the most effective pair of dissimilar metals to produce electricity waszinc andsilver. In the 1880s, theInternational Electrical Congress, now theInternational Electrotechnical Commission (IEC), approved the volt for electromotive force. The volt was defined as the potential difference across a conductor when a current of oneampere dissipates onewatt of power.
