Heat and Power
. A conductor’s resistance to electric current produces heat. The greater the current passing through the conductor, the greater the heat. Also, the greater the resistance, the greater the heat. A current of I amp passing through a resistance of R ohms for t seconds generates an amount of heat equal to joules (a joule is a unit of energy equal to 0.239 calorie). Energy is required to drive an electric current through a resistance. This energy is supplied by the source of the current, such as a battery or an electric generator. The rate at which energy is supplied to a device is called power, and it is often measured in units called watts. The power P supplied by a current of I amp passing through a resistance of R ohms is given by .