# Susceptance

In electrical engineering, the susceptance (B) is the imaginary part of the admittance. In SI units, the susceptance is measured in siemens. In June of 1887, Oliver Heaviside used the term "permittance" which later became susceptance.

## Mathematics

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

where

Y is the admittance, measured in siemens

G is the conductance, measured in siemens

[itex]j = \sqrt{-1} \, [itex]

B is the susceptance, measured in siemens.

The admittance (Y) is the inverse of the impedance (Z)

[itex]Y = 1/Z \,[itex]

where

[itex]Z = R + j X \,[itex]

Z is the impedance, measured in ohms

R is resistance, measured in ohms

X is the reactance, measured in ohms.

Note: The susceptance is NOT the inverse of the reactance.

The magnitude of admittance is given by:

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

## SI electricity units

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