Watt

Watt is a unit of power in the metric system. Power is the rate of producing or using energy. The symbol for the watt is W. The watt is commonly used to measure electric power, even in countries that have not adopted the metric system. An electric device uses 1 watt when 1 volt of electric potential drives 1 ampere of current through it. The number on a light bulb shows its power requirement in watts. For example, a light bulb operating at 100 volts and using 2 amperes consumes 200 watts (100 volts X 2 amperes). Often, power is measured in kilowatts. One kilowatt equals 1,000 watts.

The watt also is used to measure mechanical power. A machine requires a power of 1 watt if it uses 1 joule of energy in 1 second. The watt was named for the Scottish engineer and inventor James Watt.

Contributor: Gregory Benford, Ph.D., Prof. of Physics, Univ. of California, Irvine.

Watt

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