The statmho is the unit of
electrical conductance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual paral ...
in the
electrostatic system of units (ESU), an extension of the
centimeter-gram-second (CGS) system to cover electrical units. It is sometimes called the statsiemens, with symbol statS.
Conversion
In the ESU system, the
permittivity of free space
Vacuum permittivity, commonly denoted (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric const ...
is set to unity by definition. This results in unit conversions to the SI system containing a power of the
speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...
, ''c'', as well as a power of 10. In the case of the statmho, the conversion from
siemens
Siemens AG ( ) is a German multinational technology conglomerate. It is focused on industrial automation, building automation, rail transport and health technology. Siemens is the largest engineering company in Europe, and holds the positi ...
(S) is given by:
[Donald Fenna, ''A Dictionary of Weights, Measures, and Units'', pp. 83–84, Oxford University Press, 2002 .]
:1
S ≘ ''c''
2 × 10
−5 s
2/m
2 × 1 statmho.
The value of ''c'' in the SI system is metres per second exactly by definition. However, in the era in which the ESU system was in use, the speed of light was determined by measurement and was taken to be approximately centimetres per second.
[
:1 statmho ≘ 1.112650 pS.][Fenna, p. 76]
The sign ≘ denotes 'correspondence' between quantities. Equality does not apply, since the systems of quantities underlying the two systems of units are mutually incompatible.
References
Centimetre–gram–second system of units
Electricity
{{Measurement-stub