Siemens (unit)

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Physical unit
Unit name Siemens
Unit symbol
Physical quantity (s) Electrical conductance
Formula symbol
system International system of units
In SI units
Named after Werner from Siemens
Derived from Volts , amps
See also: Ohm
Resistance normal from Werner von Siemens . Double-coiled glass tube, originally filled with mercury . Around 1860.

Siemens is the unit of measurement for electrical conductance in the SI and is named after Werner von Siemens . The conductance 1 S is the reciprocal of the electrical resistanceΩ . The ohm is the SI unit of electrical resistance:

In 1860 Siemens had published the article Proposal for a reproducible resistance measure in Poggendorff's Annalen der Physik und Chemie , for details see under Ohm . At the 14th General Conference on Weights and Measures in 1971, it was decided to introduce the unit of measurement.


Mho is an outdated name for the Siemens unit , the name goes back to William Thomson . The designation Mho ( ohms read backwards) and the symbol ℧ (an upside-down large omega ) express that it is the reciprocal of the unit ohm. They were used until the 1930s, and informally in the USA in the field of electronics.

Individual evidence

  1. Werner Siemens: Proposal for a reproducible measure of resistance . In: Annals of Physics and Chemistry . tape 186 , no. 5 , 1860, p. 1-20 , doi : 10.1002 / andp.18601860502 .
  2. ^ Minutes of the 14th General Conference on Weights and Measures , 1971, p. 78, accessed Nov. 11, 2019
  3. William Maver: American Telegraphy and Encyclopedia of the Telegraph: Systems, Apparatus, operation , 1903rd