The unit of energy in SI. Symbol, J. The work done when the point of application of a force of 1 newton is displaced 1 meter in the direction of the force. One watt-second is equal to 1 joule.
The joule’s dimensions are force × length (newton × meter, or in terms of base units only:)
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The joule is named for James Prescott Joule (1818 – 1889), who in 1845 was the first to measure the equivalence of work and heat, by using falling weights to rotate paddles in water and measuring the rise in temperature of the water.
The joule was adopted in 1889 by the International Electrical Congress. When the CGPM first defined SI, in 1960, it included the joule as one of the derived units.
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Last revised: 20 August 2003.