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In electrical engineering, the admittance (Y) is the inverse or reciprocal of the impedance (Z). The SI unit of Admittance is the siemens.

Y = Z^{-1} = 1/Z \,


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

Y = G + j B \,

The magnitude of admittance is given by:

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


G is the conductance, measured in siemens

B is the susceptance, measured in siemens

SI electricity units

SI electromagnetism units

Name Symbol Dimensions Quantity
ampere (SI base unit) A C / s Current
coulomb C A · s Electric charge, Quantity of electricity
volt V J / C = kg m2 / (s2 C) Potential difference
ohm Ω V / A = kg m2 / (C2) Resistance, Impedance, Reactance
ohm &middot metre Ω &middot m kg m3 / (C2) Resistivity
farad F C / V = C2 s / (kg m2) Capacitance
farad per metre F / m C2 s / (kg m3) Permittivity
reciprocal farad F−1 kg m2 / (C2 s) Elastance
siemens S Ω−1 = C2 / (kg m2) Conductance, Admittance, Susceptance
siemens per metre S / m C2 / (kg m3) Conductivity
weber Wb V &middot s = kg m2 / (C s) Magnetic flux
tesla T Wb / m2 = kg / (C s) Magnetic flux density
ampere / metre A / m C / (s m) magnetic induction
ampere-turns / weber A / Wb C2 / (kg m2) Reluctance
henry H V &middot s / A = kg m2 s / (C2) Inductance
henry per metre H / m kg m s / (C2) Permeability
(dimensionless) - - Magnetic susceptibility

External links

  • Conductance, Susceptance, and Admittance

Last updated: 02-08-2005 13:10:00
Last updated: 05-02-2005 19:44:03