# Electric Circuits - Mission EC3 Detailed Help A light bulb does 300 Joules of work over a 5 second time period. What is the power of the light bulb? Definition of Power: Power is the rate at which work is done upon an object. As applied to electrical circuits, electrical power is the rate at which work is done upon a charge. The work done upon a charge results in a change in the electric potential energy of the charge. Thus, power can be defined in electrical terms as the rate at which a charge changes its electric potential energy. Power (P) is the rate at which a charge changes its electric potential energy (∆E) as it moves from one location to another location. This can be expressed as   P = ∆E / t. Light bulbs have a power rating. The power rating describes the rate at which the light bulbs uses the electrical energy of moving charge to produce light energy (and thermal energy). A 60-Watt bulb will consume 60 J of electrical energy per second of time when plugged into a typical U.S. outlet. As descried in the Formula Frenzy section, the power rating is simply the ratio of energy used per time of use.  