The joule (J) is the SI unit of energy and work, and is defined as 1 kgm2s-2 = 1 Nm = 1 Ws. It is named in honour of the physicist James Prescott Joule.

One joule is the work required to exert a force of one newton for a distance of one metre, so the same quantity may be referred to as a newton metre. However, to avoid confusion the newton metre is usually used as a measure of torque, not energy. Another way of visualizing the joule is the work required to lift a mass of 102 g (e.g. a small apple) for one metre under the earth's gravity.

One joule is also the work done to produce power of one watt for one second, such as when somebody takes one second to lift the small apple mentioned above through one metre under the earth's gravity.

1 joule is equal to:

  • 0.000,000,278 kilowatt hours
  • 0.239 calories
  • 0.000,948 British thermal units
  • 0.738 foot pounds force
  • 1 Ws (watt second)
  • 1 Nm (newton metre)
  • 23.7 foot poundals
  • 10,000,000 ergs

See 1 E0 J for further comparisons.

See also: conversion of units, eV, kWh, TWh

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