If a current, I, is passed through a circuit of resistance R, electrical energy is dissipated as the current flows from a higher to a lower potential. The rate of dissipation of energy equals I2R. This is known as I2R loss. The energy appears as heat; if all the electrical energy is converted into a quantity of heat Q, then
where t is the time for which the current flows. The temperature does not increase indefinitely since a stable state is reached when the rate of emission from the surface of the resistor just equals the rate of generation of heat.