"Such a heat unit, if found acceptable, might with great propriety, I think, be called the Joule, after the man who has done so much to develop the dynamical theory of heat." Īt the second International Electrical Congress, on 31 August 1889, the joule was officially adopted alongside the watt and the quadrant (later renamed to henry). The naming of the unit in honour of James Prescott Joule (1818–1889), at the time retired but still living (aged 63), is due to Siemens: Wilhelm Siemens, in his inauguration speech as chairman of the British Association for the Advancement of Science (23 August 1882) first proposed the Joule as unit of heat, to be derived from the electromagnetic units Ampere and Ohm, in cgs units equivalent to 10 7 erg. The erg was adopted as its unit of energy in 1882. The cgs system had been declared official in 1881, at the first International Electrical Congress. 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. The joule is named after James Prescott Joule. This relationship can be used to define the watt. The work required to produce one watt of power for one second, or one watt-second (W⋅s) (compare kilowatt-hour, which is 3.6 megajoules).This relationship can be used to define the volt. 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).One joule can also be defined by any of the following: J = k g ⋅ m 2 ⋅ s − 2 = N ⋅ m = P a ⋅ m 3 = W ⋅ s = C ⋅ V
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