# Siemens (unit)

Physical unit
Unit name Siemens
Unit symbol ${\ displaystyle \ mathrm {S}}$
Physical quantity (s) Electrical conductance
Formula symbol ${\ displaystyle G}$
dimension ${\ displaystyle {\ mathsf {M ^ {- 1} \; L ^ {- 2} \; T ^ {3} \; I ^ {2}}}}$
system International system of units
In SI units ${\ displaystyle \ mathrm {1 \, S = 1 \; {\ frac {A ^ {2} \, s ^ ​​{3}} {kg \, m ^ {2}}} = 1 \; {\ frac { A} {V}}}}$
Named after Werner from Siemens
Derived from Volts , amps
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:

${\ displaystyle \ mathrm {S = {\ frac {1} {\ Omega}} = {\ frac {A} {V}}}}$

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

Mho is an outdated name for the Siemens unit , the name goes back to William Thomson .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