The siemens (symbol: S) is an SI derived unit of measurement for electric conductance, being the inverse of the ohm (Ω), named after Werner von Siemens.
S = A / V
- S = Siemens
- A = Amperes
- V = Volts
- The forumla for computing conductance is as follows:
G = 1 / R = S
- G = Conductance
- R = Resistance (Ω)
- S = Siemens
Example: G = 1 / 6 Ω = 0.1667 S
Mho is a now eccentric name for this unit of electrical conductance, equal to 1 Ω−1. It is derived by spelling ohm backwards. Its symbol is 
(the upside-down letter Ω). The term siemens is used universally in science and primarily in electrical applications, while mho is used primarily in electronic applications.
SI electricity units