In electrical engineering, the admittance (Y) is the inverse or reciprocal of the impedance (Z). The SI unit of Admittance is the siemens. In December of 1887, Oliver Heaviside coined this term.

[itex]Y = Z^{-1} = 1/Z \,[itex]

where

Y is the admittance, measured in siemens

Z is the impedance, measured in ohms

Just as impedance is complex resistance, and the conductance G is the inverse G = 1/R of resistance R, admittance is also complex conductance.

Likewise, admittance is made up of a real part (the conductance), and an imaginary part (the susceptance B), shown by the equation

[itex]Y = G + j B \,[itex]

The magnitude of admittance is given by:

[itex]\left | Y \right | = \sqrt {G^2 + B^2} \,\![itex]

where

G is the conductance, measured in siemens

B is the susceptance, measured in siemens

## SI electricity units

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