Electric power is defined as the amount of work per second done by an electric current, or the rate at which electrical energy is transmitted. The SI unit of power is the watt, which equals one joule per second.
When electric current flows in a circuit with resistance, it does work. Devices convert this work into many useful forms, such as heat (electric heaters), light (light bulbs), motion (electric motors) and sound (loudspeaker).
- Reports on August 2003 Blackout, North American Electric Reliability Council website
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