The SI unit of voltage is the volt, named after Italian scientist Alessandro Volta.
A volt measures electric potential difference: one volt is the potential difference that causes one ampere of current to carry one joule of energy per coulomb. In circuit terms, voltage provides the electrical push that can drive current through a resistance.
Volta developed the voltaic pile around 1800, generally regarded as the first practical battery. His work helped establish that electricity could be produced continuously by chemical reactions rather than only by static charge or brief sparks.
The volt is often confused with the ampere and ohm. The ampere measures current, while the ohm measures resistance; their relationship is expressed by Ohm’s law, V = IR. Household outlets, batteries, and electronic circuits are all described using voltage values.