Jar (unit)

{{Verification|date=October 2023}}{{Infobox Unit | bgcolour = | name = Jar | image = | caption = | standard = | quantity = Capacitance | symbol = | dimension = M−1⋅L−2⋅T4⋅I2  <ref name="eFunda: Glossary: Units: Electric Capacitance: Jar">{{cite web |title=eFunda: Glossary: Units: Electric Capacitance: Jar |url=http://www.efunda.com/glossary/units/units--electric_capacitance--jar.cfm |publisher=eFunda |accessdate=22 May 2012 }}</ref> | namedafter = }} A '''jar''' was an early unit of capacitance once used by the British Royal Navy.<ref name="Handbook"> {{cite book | title = Admiralty Handbook of Wireless Telegraphy | publisher = H. M. Signal School, British Admiralty | date = 1931 | location = London | pages = [https://archive.org/details/AdmiraltyHandbookOfWirelessTelegraphy1931/page/n131 119] | language = | url = https://archive.org/details/AdmiraltyHandbookOfWirelessTelegraphy1931 | doi = | id = | isbn = }}</ref> The term originated as the capacitance of a Leyden jar. Its value is such that one farad is {{val|9|e=8}} jars and one jar is 1111 picofarads.<ref name="Metal Pass, English-Metric Unit Conversion Table – Electric and Magnetic">{{cite web |title=English–Metric Unit Conversion Table – Electric and Magnetic |url=http://www.metalpass.com/unit/unit9.aspx |publisher=Metal Pass |date= 2002 |accessdate=2 September 2022 |archive-url=https://web.archive.org/web/20150720223538/http://www.metalpass.com/unit/unit9.aspx |archive-date=20 July 2015 |url-status=dead }}</ref>

== History == With early spark-gap transmitters, changing the transmission frequency was most easily accomplished by changing the number of Leyden jars connected to the tank circuit. While it was possible to calculate the required capacitance directly, it was more usual to simply have a book of lookup tables which gave the number of jars needed for any likely wavelength.

== References == {{reflist}}

Category:Units of electrical capacitance