Joule (J) is the unit of electrical, mechanical and thermal energy in the international system of units.
As electrical energy, one joule is equal to the work done by a current of one ampere flowing through a resistor of one ohm for one second. Thus, one joule is equal to one watt-second (Ws), or 3,600 joules are equal to one watt-hour. This in turn corresponds to 860 calories (cal).
This irreversible generation of energy, based on thermoelectrics, is also known as the Joule effect. The joule is named after the British physicist James Prescott Joule (1818 - 1889).