The 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 with the symbol N·m. However, the newton metre is usually used as a measure of work.
Definition[επεξεργασία | επεξεργασία κώδικα]
As a rough guide, 1 joule is the absolute minimum amount of energy required to lift a one kilogram object up by a height of 10 centimetres on the surface of the Earth.
Other definitions[επεξεργασία | επεξεργασία κώδικα]
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
Conversions[επεξεργασία | επεξεργασία κώδικα]
1 joule is exactly 107 ergs.
1 joule is approximately equal to:
- 6.24150636309 Πρότυπο:E eV (electron-volts)
- 0.238845896628 cal (calorie) (small calories)
- 2.390 Πρότυπο:E kilocalorie (food)
- 9.47817120313 Πρότυπο:E BTU (British thermal unit)
- 0.737562149277 ft·lbf (foot-pound force)
- 23.7 ft·pdl (foot poundals)
- 2.7778 Πρότυπο:E kilowatt-hour
- 2.7778 Πρότυπο:E watt-hour
- 9.8692 Πρότυπο:E litre-atmosphere
Also, some very rough approximations of a joule from the real world are:
- the energy required to lift a small apple (102 g) one metre against Earth's gravity.
- the amount of energy, as heat, that a quiet person produces every hundredth of a second.
- the energy required to heat one gram of dry, cool air by 1 degree Celsius.
- 1/100th of the energy a person can get by drinking a single droplet of beer.
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)
History[επεξεργασία | επεξεργασία κώδικα]
A joule is the mechanical equivalent of heat meaning the number of units of work in which the unit of heat can perform. Its value was found by Joule James-Prescott in experiments that showed the mechanical energy Joule's equivalent, and represented by the symbol J. The term was first introduced by Dr. Mayer of Heilbronn.