watt (redirected from Watt (unit))

watt [for James Watt], abbr. W, unit of power, or work done per unit time, equal to 1 joule per second. It is used as a measure of electrical and mechanical power. One watt is the amount of power that is delivered to a component of an electric circuit when a current of 1 ampere flows through the component and a voltage of 1 volt exists across it. The derivative units are kilowatt (1,000 W; kW) and megawatt (1,000,000 W; MW), used in electric power systems, and milliwatt (0.001 W; mW) and microwatt (0.000001 W; μW), used in electronics.

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The standard unit of measurement of electrical power. One watt is one ampere of current flowing at one volt. Watts are typically rated as AMPS x VOLTS or VOLT-AMP (V-A). However, this rating is only equivalent to watts when it applies to devices that absorb all the energy, such as electric heating coils or incandescent light bulbs. With computer power supplies, the actual watt rating is only 60% to 70% of the VOLT-AMP rating.