Volt

The volt (symbol V) is the SI unit of electric potential difference. By definition, a potential difference of one volt between two points means that one joule of work is done per coulomb of charge moved between them. Equivalently: 1 V = 1 J/C = 1 kg·m²·s⁻³·A⁻¹ in SI base units.

Volts are the everyday currency of electricity. A flashlight battery delivers 1.5 V across its terminals. Car batteries deliver 12 V. Household wall outlets supply 110–240 V depending on country. High-voltage transmission lines run at hundreds of kilovolts. The van de Graaff generators used in particle physics reach several megavolts. At the low end, the signals inside a neuron move around in tens of millivolts.

The unit honours Alessandro Volta, who in 1800 invented the voltaic pile — a stack of zinc and copper discs separated by brine-soaked cloth — and thereby produced the first steady electric current in human history. Before Volta, every electrical experiment had to be powered by sparks and Leyden jars; after him, steady currents made electrochemistry, electromagnetism, and eventually electric power possible.