1) The practical mks unit of electrical potential difference and electromotive force equal to the difference of potential between two points in a conducting wire carrying a constant current of one ampere when the power dissipated between these two points is equal to one watt and equivalent to the potential difference across a resistance of one ohm when one ampere is flowing through it.

2) A unit of electrical potential difference and electromotive force equal to 1.00034 volts and formerly taken as the standard in the United States. Volta, Alessandro Giuseppe Antonio Anastasio (1745-1827), Italian physicist. Volta served as professor of physics at the University of Pavia, Italy, from 1779 to 1804. From 1815 he was director of the philosophical faculty at the University of Padua, Italy. His interest in electricity led him to invent in 1775 a device used to generate static electricity. In 1800 he demonstrated his electric battery for the first time. The volt, a unit of potential difference that drives current, was named in his honor.