Watt

==Overview==
When an object's [[velocity]] is held constant at one [[meter per second]] against a constant opposing force of one [[Newton (unit)|newton]], the rate at which [[Work (physics)|work]] is done is one watt.
<math display=block>\mathrm{1 ~ W = 1 ~ J {/} s = 1 ~ N {\cdot} m {/} s = 1 ~ kg {\cdot} m^2 {\cdot} s^{-3}}.</math>

In terms of [[electromagnetism]], one watt is the rate at which [[electrical work]] is performed when a current of one [[ampere]] (A) flows across an electrical [[potential difference]] of one [[volt]] (V), meaning the watt is equivalent to the [[volt-ampere]] (the latter unit, however, is used for a different quantity from the [[real power]] of an electrical circuit).
<math display=block>\mathrm{1 ~ W = 1 ~ V \times 1 ~ A}.</math>

Two additional [[Conversion of units|unit conversions]] for watt can be found using the above equation and [[Ohm's law]].
<math display=block>\mathrm{1 ~ W = 1 ~ V^2 / \Omega = 1 ~ A^2 {\cdot} \Omega},</math>
where [[ohm]] (<math>\Omega</math>) is the [[SI derived unit]] of [[electrical resistance]].

=== Examples ===
*A person having a mass of 100&nbsp;kg who climbs a 3-meter-high ladder in 5 seconds is doing work at a rate of about 600 watts. Mass times acceleration due to [[gravity]] times height divided by the time it takes to lift the object to the given height gives the ''rate of doing work'' or ''power''.{{efn-lr|The energy in climbing the stairs is given by {{mvar|mgh}}. Setting {{math|''m'' {{=}} 100 kg}}, {{math|''g'' {{=}} 9.8 m/s<sup>2</sup>}} and {{math|''h'' {{=}} 3 m}} gives 2940&nbsp;J.  Dividing this by the time taken (5&nbsp;s) gives a power of 588&nbsp;W. }}
* A laborer over the course of an eight-hour day can sustain an average output of about 75 watts; higher power levels can be achieved for short intervals and by athletes.<ref>{{Citation | editor1-first = Eugene A | editor1-last = Avallone |display-editors=etal | year = 2007 | title = Marks' Standard Handbook for Mechanical Engineers | edition = 11th | publisher = Mc-Graw Hill | place = New York | isbn = 978-0-07-142867-5 | pages = 9–4}}.</ref>