The joule (symbol: J) is the SI unit of energy, or work. It is named in honour of the physicist James Prescott Joule (1818–1889). DefinitionThe joule is a derived unit defined as the work done, or energy 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 or newton-metre (also with meter spelling), with the symbol N·m or N m. It can also be written as kg·m2·s−2. However, the newton metre is usually used as a measure of torque, not energy. For a rough guide, 1 joule is the absolute minimum amount of energy required (on the surface of Earth) to lift an one kilogram object up by a height of 10 centimetres. One joule is also: - The work required to move an electric charge of one coulomb through an electrical potential difference of one volt; or one coulomb volt, with the symbol C·V.
- The work done to produce power of one watt continuously for one second; or one watt second (compare kilowatt-hour), with the symbol W·s
The work done to raise the temperature of a unit of water by 1 degree celcuis. |
