The siemens, abbreviated S, is the SI unit of electrical conductance. It is the conductance which will allow a current of one ampere across a potential drop of one volt. The siemens is the reciprocal of the ohm.
 Siemens and mho
Before the BIPM approved the siemens as a derived unit in 1971, the common unit for conductance was the mho (ohm spelled backwards), abbreviated ℧. The mho is still in use, despite not having official status, as the upside-down omega is not likely to be confused with lower-case s for seconds, nor for S occurring in formulas.
- Siemens. Sizes.com (2004-12-06). Retrieved on 2007-06-23.
- Mho. Sizes.com (2007-04-21). Retrieved on 2007-06-23.
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