# Volt

SI unit of voltage

The volt (symbol: V) is the SI derived unit of electric potential difference or electromotive force (also known as voltage). It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, the first chemical battery.

For the electric plug-in hybrid concept car, see Chevrolet Volt.
For the record label, see Volt Records

## Definition

The volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power. Hence, it is the base SI representation m2 · kg · s−3 · A−1, which can be equally represented as one joule of energy per coulomb of charge, J/C.

${\mbox{V}}={\dfrac {\mbox{W}}{\mbox{A}}}={\dfrac {\mbox{J}}{\mbox{C}}}={\dfrac {{\mbox{m}}^{2}\cdot {\mbox{kg}}}{{\mbox{s}}^{3}\cdot {\mbox{A}}}}$

## Hydraulic analogy

In the hydraulic 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 the volume 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

## Common voltages

Note: Where 'RMS' (root mean square) is stated above, the peak voltage is ${\sqrt {2}}$  times greater than the RMS voltage for a sinusoidal signal.