Jar (unit)

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Jar
Unit of Capacitance

A jar was an early unit of capacitance once used by the Royal Navy.[1] The term relates to the capacitance of a Leyden jar.

Its value is such that one farad is 9.000×108 jars and one jar is 1111 picofarads.[2]

History[edit]

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[edit]

  1. ^ Admiralty Handbook of Wireless Telegraphy, 1931, p.119. HMSO, London.
  2. ^ "Metal pass, English-Metric Unit Conversion Table - Electric and Magnetic". Metal Pass. Retrieved 22 May 2012.