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 about 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:
- c. 2.78 × 10−7 kWh
- c. 0.239 cal
- c. 0.000,948 BTU
- c. 0.738 ft lbf (foot pound force)
- 1 Ws (watt second)
- 1 Nm (newton metre)
- c. 23.7 ft pdl (foot poundal)
- 10,000,000 erg
It is named in honour of the physicist James Prescott Joule.