Coulomb (coul or C), unit of electricity, the quantity of electricity that must pass through a circuit to deposit .0000394 oz (0.0011180 g) of silver from a solution of silver nitrate. It is named for French physicist Charles Augustin de Coulomb. An ampere is 1 coulomb per second. A coulomb is also the quantity of electricity on the positive plate of a condenser of 1-farad capacity when the electromotive force is 1 volt.
See also: Ampere.