VOLT

The volt (symbol V) is the SI unit of electric potential difference, electric potential, and electromotive force. It is a derived unit used to quantify the work needed to move electric charges or the energy delivered per unit charge in an electrical circuit. The volt is named after Alessandro Volta, the 18th–19th century Italian physicist who invented the voltaic pile, an early chemical battery.

Definition and relations: The volt is defined so that one volt is the potential difference between two points of a conductor when a constant current of one ampere, passing through the conductor, dissipates one watt of electrical power between those points. Equivalently, 1 V = 1 joule per coulomb (1 J/C). In circuit terms, voltage relates to current and resistance through P = VI and V = IR. In modern practice, the volt is realized internationally through quantum electrical standards, linking voltage to fundamental constants.

Submultiples and usage: Common prefixes yield microvolts (µV), millivolts (mV), kilovolts (kV), and megavolts (MV). The volt is used to express household and industrial voltages, electrical instrument readings, and the potential differences in circuits.

Measurement and standards: Voltage is measured with a voltmeter or a volt-typically connected in parallel to the component under test. Since the 2019 redefinition of SI base units, the volt is defined through fixed fundamental constants and realized in practice via quantum electrical standards, such as the Josephson effect, ensuring precise and reproducible voltage measurements.