Joule


 * joule ****, ** unit of [|work] or energy in the [|International System of Units] (SI); it is equal to the [|work] done by a [|force] of one [|newton] acting through one metre. Named in honour of the English physicist [|James Prescott Joule], it equals 107 [|ergs] , or approximately 0.7377 foot-pounds. In electrical terms, the joule equals one watt-second—i.e., the energy released in one[|second] by a current of one [|ampere] through a resistance of one [|ohm].

In terms firstly of base SI units and then in terms of other SI units: where N is the [|newton], m is the [|meter] , kg is the [|kilogram] , s is the [|second] , Pa is the [|pascal] , and W is the [|watt]. One joule can also be defined as: 1 joule is equal to: Units defined exactly in terms of the joule include:
 * The work required to move an [|electric charge] of one [|coulomb] through an [|electrical potential difference] of one [|volt], or one '"coulomb volt" (C·V). This relationship can be used to define the volt.
 * The work required to produce one [|watt] of [|power] for one [|second], or one "watt second" (W·s) (compare [|kilowatt hour] ). This relationship can be used to define the watt.
 * __Conversions__**
 * 1×107 [|ergs] (exactly)
 * 6.24150974×1018 eV ([|electronvolts])
 * 0.2390 cal (thermochemical gram [|calories] or small calories)
 * 2.3901×10−4 kcal (thermochemical kilocalories, kilogram calories, large calories or [|food calories])
 * 9.4782×10−4 BTU ([|British thermal unit])
 * 0.7376 ft·lbf ([|foot-pounds 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]
 * 11.1265 [|femtograms] ([|mass-energy] equivalence)
 * 1×10−44 [|foe] (exactly)
 * 1 thermochemical calorie = 4.184 J
 * 1 International Table calorie = 4.1868 J
 * 1 watt hour = 3600 J
 * 1 kilowatt hour = 3.6×106 J (or 3.6 MJ)
 * 1 watt second = 1 J
 * 1 [|ton TNT] = 4.184 GJ

Confusion with newton metre
Although the joule has the same dimensions as the newton-metre (1 J = 1 N·m = 1 kg·m2·s−2), these units are //not// interchangeable as the newton-metre (N·m) is the unit of [|torque] and joules the unit of [|energy]. [|[4]] Torque and energy are related to each other using the equation where //E// is the energy, //τ// is magnitude of the torque, and //θ// is the angle moved (in [|radians] ). Since radians are dimensionless, it follows that torque and energy have the same dimensions. The use of newton-metres for torque and joules for energy is useful in helping avoid misunderstandings and miscommunications. [|[4]] Torque and energy have the same dimension because both torque and [|work] (a type of energy) can be calculated by multiplying a force by a distance. However, the details are quite different in the two cases. For torque, the multiplication of force and distance is a [|vector cross product], while for work it is a [|dot product]. Also, for torque, the distance involved is the length of the [|lever arm], while for energy it is the distance traveled by the object undergoing the force.