= Siemens
{disambiguate=unit}
{title2=$\mathrm S=\Omega^{-1}$}
{wiki}
= Siemens
{synonym}
The <siemens>, symbol $\mathrm S$, is the <SI> unit of <electrical conductance> and <electrical admittance>: $1\,\mathrm S=1\,\mathrm{A/V}=1\,\Omega^{-1}$. A conductance of $2\,\mathrm S$ corresponds to resistance $0.5\,\Omega$ for an ideal <resistor>.
The same unit can describe a complex <electrical admittance> in a sinusoidal experiment; that value includes a reactive part as well as conductance. For a uniform conducting sample, <electrical conductivity> instead has units $\mathrm{S\,m^{-1}}$ because the conversion from material response to conductance also involves sample <area> and <length>.
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