Joule
311pages on
this wiki
Add New Page
this wiki
This page uses content from the Engineering wiki on Wikia. The original article was at Joule. The list of authors can be seen in the page history. As with the Units of Measurement wiki, the text of the engineering wiki is available under Creative Commons License see Wikia:Licensing. |
The joule (symbol: J) is the SI unit of energy, or work. It is named in honor of the physicist James Prescott Joule (1818–1889).
DefinitionEdit
The 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 meter, so the same quantity may be referred to as a newton meter or newton-meter (also with metre spelling), with the symbol N·m or N m. It can also be written as kg·m^{2}·s^{−2}. However, the newton meter is usually used as a measure of torque, not energy.
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
ConversionsEdit
1 joule is exactly 10^{7} erg.
1 joule is approximately equal to:
- 6.241506363 × 10^{18} eV (electron-volts)
- 0.239 cal (calorie) (small calories)
- 2.390 × 10^{-4} Calorie or kilocalorie (food)
- 9.48 × 10^{-4} BTU (British thermal unit)
- 0.738 ft·lbf (foot pound force)
- 23.7 ft·pdl (foot poundals)
- 2.7778 × 10^{-7} kilowatt-hour
- 2.7778 × 10^{-4} watt-hour
- 9.8692 × 10^{-3} litre-atmosphere
- the energy required to lift a small apple (102 g) one meter against Earth's gravity
Units defined in terms of the joule include:
- 1 thermochemical calorie = 4.184 J (exact)
- 1 International Table calorie = 4.1868 J (exact)
- 1 watt-hour = 3600 J (exact)