View source for Erdős–Ko–Rado theorem

In [[electrical engineering]], '''susceptance''' (''B'') is the imaginary part of [[admittance]]. The inverse of admittance is [[Electrical impedance|impedance]] and the real part of admittance is [[Electrical conductance|conductance]]. In [[SI]] units, susceptance is measured in [[siemens (unit)|siemens]]. [[Oliver Heaviside]] first defined this property, which he called ''permittance'', in June 1887.<ref>{{cite book|last=Heaviside|first=Oliver|title=Electrical Papers, Volume 2|year=1892|publisher=Macmillan and Co.|location=London and New York|url=http://books.google.com/books?id=bywPAAAAIAAJ&pg=PA330&lpg=PA330&dq=oliver+heaviside+permittance&source=bl&ots=yYSnHP1fd2&sig=-QAvwPIN_8sjE0UUSh5mYC9tLWw&hl=en&sa=X&ei=zHAyUby2LeGo2wWq4oH4Dg&ved=0CEcQ6AEwBA#v=onepage&q=oliver%20heaviside%20permittance&f=false}}</ref>

==Formula==
The general equation defining admittance is given by
:<math>Y = G + j B \,</math>

where
:''Y'' is the [[admittance]], measured in siemens (a.k.a. mho, the inverse of ohm).
:''G'' is the [[Electrical conductance|conductance]], measured in siemens.
:''j'' is the [[imaginary unit]], and
:''B'' is the susceptance, measured in siemens.

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

:<math>Y = \frac {1} {Z} = \frac {1} {R + j X} = \left( \frac {R} {R^2+X^2} \right) + j \left( \frac{-X} {R^2+X^2} \right) \,</math>

or
:<math>B = Im(Y) = \left( \frac{-X} {R^2+X^2} \right) = \frac{-X}{|Z|^2}</math>

where

:<math>Z = R + j X \,</math>
:''Z'' is the [[electrical impedance|impedance]], measured in [[Ohm (unit)|ohms]]
:''R'' is the [[electrical resistance|resistance]], measured in ohms
:''X'' is the [[Reactance (electronics)|reactance]], measured in ohms.

Note: The susceptance is the imaginary part of the admittance.

The magnitude of admittance is given by:

:<math>\left | Y \right | = \sqrt {G^2 + B^2} \,</math>

==See also==
*[[Electrical measurements]]
*[[SI electromagnetism units]]

== References ==
{{reflist}}

<!--Categories-->
[[Category:Physical quantities]]
[[Category:Electrical engineering]]