In electrical engineering, the susceptance (B) is the imaginary part of the admittance. In SI units, the susceptance is measured in siemens. Oliver Heaviside first defined this property, which he called permittance, in June 1887[citation needed].
The general equation defining admittance is given by
where
Rearranging yields
But since
we obtain
The admittance (Y) is the inverse of the impedance (Z)
or
where
Note: The susceptance is the imaginary part of the admittance.
The magnitude of admittance is given by: