|unit system||si derived unit|
|named after||james prescott joule|
|1 j in ...||... is equal to ...|
| si base units|| kg⋅m2⋅s−2|
| cgs units|| 1×107 erg|
| kilowatt hours|| 2.78×10−7 kw⋅h|
| kilocalories (thermochemical)|| 2.390×10−4 kcalth|
| btus|| 9.48×10−4 btu|
| electronvolts|| 6.24×1018 ev|
the joule (/ jawl, jool; symbol: j) is a derived unit of energy in the international system of units. it is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre (1 newton metre or n⋅m). it is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. it is named after the english physicist james prescott joule (1818–1889).
in terms firstly of base si units and then in terms of other si units, a joule is defined below (please consider this table for the meaning of symbols):
one joule can also be defined as the following:
- 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 – 3.6 megajoules). this relationship can be used to define the watt.
the joule is named after james prescott joule. as with every si unit named for a person, its symbol starts with an upper case letter (j), but when written in full it follows the rules for capitalisation of a common noun; i.e., "joule" becomes capitalised at the beginning of a sentence and in titles, but is otherwise in lower case.