Watt

==Origin and adoption as an SI unit==
The watt is named after the Scottish inventor [[James Watt]].<ref name=Klein>{{cite book |last=Klein |first=Herbert Arthur |year=1988 |location=New York |publisher=Dover |orig-year=1974 |title=The Science of measurement: A historical survey |isbn=9780486144979 |page=239 }}</ref> The unit name was proposed by [[Carl Wilhelm Siemens|C. William Siemens]] in August 1882 in his President's Address to the Fifty-Second Congress of the [[British Science Association|British Association for the Advancement of Science]].<ref name=Siemens>{{cite encyclopedia |url=https://www.biodiversitylibrary.org/item/95237#page/85/mode/1up |title= Address by C. William Siemens|pages=1–33|encyclopedia= Report of the Fifty-Second meeting of the British Association for the Advancement of Science |location=London| publisher = John Murray | year = 1883 |volume= 52}}</ref> Noting that units in the [[CGS#Practical cgs units|practical system of units]] were named after leading physicists, Siemens proposed that ''watt'' might be an appropriate name for a unit of power.<ref>Siemens supported his proposal by asserting that  Watt was the first who "had a clear physical conception of power, and gave a rational method for measuring it." [https://www.biodiversitylibrary.org/item/95237#page/90/mode/1up "Siemens, 1883, p. 6"]</ref> Siemens defined the unit within the existing system of practical units as "the power conveyed by a current of an [[Ampere|Ampère]] through the difference of potential of a Volt".<ref>{{Cite web|url=https://www.biodiversitylibrary.org/item/95237|title=Report of the British Association for the Advancement of Science|date=April 3, 1883|volume=52nd Meeting (1882)}}</ref>

In October 1908, at the International Conference on Electric Units and Standards in London,<ref>{{cite book | author=Tunbridge, P. | title=Lord Kelvin: His Influence on Electrical Measurements and Units | location=Peter Peregrinus | publisher=London | year=1992 |page=51 | isbn=0-86341-237-8}}</ref> so-called ''international'' definitions were established for practical electrical units.<ref name=EB11-742>{{cite EB1911|wstitle= Units, Physical | volume= 27 | pages = 738&ndash;745; see page 742 |last= Fleming |first= John Ambrose |author-link= John Ambrose Fleming}}</ref> Siemens' definition was adopted as the ''international'' watt. (Also used: {{nowrap|1 A<sup>2</sup> ×}} 1&nbsp;Ω.)<ref name=Klein/> The watt was defined as equal to 10<sup>7</sup> units of power in the ''practical system'' of units.<ref name=EB11-742/> The [[International System of Electrical and Magnetic Units#Overdefinition and the 1908 modification|"international units"]] were dominant from 1909 until 1948. After the 9th [[General Conference on Weights and Measures]] in 1948, the ''international'' watt was redefined from practical units to absolute units (i.e., using only length, mass, and time). Concretely, this meant that 1 watt was defined as the quantity of energy transferred in a unit of time, namely 1&nbsp;J/s. In this new definition, 1 ''absolute'' watt&nbsp;= 1.00019 ''international'' watts. Texts written before 1948 are likely to be using the ''international'' watt, which implies caution when comparing numerical values from this period with the post-1948 watt.<ref name=Klein/> In 1960, the 11th General Conference on Weights and Measures adopted the ''absolute'' watt into the [[International System of Units]] (SI) as the unit of power.<ref>{{cite web |url=https://www.bipm.org/en/CGPM/db/11/12/ |title= Resolution 12 of the 11th CGPM (1960)|author=<!--Not stated--> |publisher=  Bureau International des Poids et Mesures (BIPM) |access-date=9 April 2018 |archive-date=April 20, 2020 |archive-url=https://web.archive.org/web/20200420104247/https://www.bipm.org/en/CGPM/db/11/12/}}</ref> 
<!--{{SI unit lowercase|James Watt|watt|W}}-->