# Electrical conductance

Physical size
Surname Electrical conductance
Formula symbol ${\ displaystyle G}$
Size and
unit system
unit dimension
SI S. I 2 · T 3 · M −1 · L −2
Gauss ( cgs ) s -1 · cm T −1 · L
esE ( cgs ) s -1 · cm T −1 · L
emE ( cgs ) abΩ −1 T · L −1

The electrical conductance is the reciprocal of the ohmic resistance and thus the parameter of an electrical component . It is not to be confused with electrical conductivity , a material constant. The symbol for the electrical conductance is , its SI unit is Siemens with the unit symbol S. ${\ displaystyle G}$

${\ displaystyle G = {\ frac {1} {R}} = {\ frac {I} {U}}}$

The physical quantity conductance can be calculated at any time from the ohmic resistance of a specific component or the values ​​of the current strength and voltage . Here are equal sizes to use or instantaneous values at varying over time sizes. ${\ displaystyle R}$ ${\ displaystyle I}$ ${\ displaystyle U}$

When a consumer conducts electricity well, it has a high conductance and a low resistance. The managing value of a body depends on its geometric dimensions and a material-specific constant, the electrical routing capability . This is the reciprocal of the specific resistance .

## Designations

The non-standard unit symbol ("Mho"; Ohm written backwards) for Siemens is often used in the field of electronics in the Anglo-American language area. ${\ displaystyle \ mho}$

With sinusoidal alternating currents and linear resistances , a complex conductance can arise, see admittance .

The term “conductance” is used both for the conductance in the sense of this article and for the effective conductance , if a reactive conductance must also be observed for alternating current .

## Geometric dimensions

For a straight conductor with conductivity , constant cross-sectional area and length, the following applies in the longitudinal direction : ${\ displaystyle \ gamma}$${\ displaystyle A}$${\ displaystyle l}$

${\ displaystyle G = \ gamma \ cdot {\ frac {A} {l}}}$

For liquids, the relationship between conductivity and conductivity is given by the design of the measuring cell. Then applies

${\ displaystyle G = \ gamma \ cdot {\ text {const}}}$

Most conductivity measuring cells have the constant const = 1.00 cm. This must be taken into account with older conductivity measuring devices (more precisely, conductance meters) whose scales are labeled in Siemens (S), Millisiemens (mS), Microsiemens (μS) or Nanosiemens (nS), but with which conductivities are actually measured. If an electrical resistor is connected to such a conductivity meter, the conductivity is displayed directly. With a connected liquid measuring cell, these older devices then measure conductivities.