Siemens mercury unit
The Siemens mercury unit is an obsolete unit of electrical resistance. It was defined by Werner von Siemens in 1860[1] as the resistance of a mercury column with a length of one metre and uniform cross-section of 1mm2 held at a temperature of zero degrees Celsius. It is equivalent to approximately 0.953 ohm.
Because glass tube cross sections are often slightly conical the unit was sometimes constructed by the weight of mercury in 1 m.[2]
The Siemens mercury unit was superseded in 1884,[3] but continued in use in some telegraph and telephone services until World War II.[citation needed]
See also
References
- ^
Werner Siemens (1860-01-01), "Vorschlag eines reproducirbaren Widerstandsmaaßes", Annalen der Physik und Chemie, vol. 186, no. 5, pp. 1–20, doi:10.1002/andp.18601860502
{{citation}}: CS1 maint: date and year (link) - ^ The Electric Telegraph. R Sabine. 1867 p331
- ^ Ohm#Historical_units_of_resistance
External links
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