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Admittance (Y) – Definition, Method & Application

Admittance (Y) – Definition, Method & Application


The correspondence of an AC circuit impedance is known as Admittance since impedance is the total resistance obtained to the flow of alternating current in an AC circuit. Therefore, Admittance is the circuit’s practical ability to allow the alternating current to flow through it. Admittance is a compound number; its actual part is conductance G, and the made-up part is susceptance B.

In general, [Admittance] is a function of frequency. Its made-up part equals zero for direct current, and the usual part equals conductance. It is represented by (Y). The old unit of Admittance is mho (Ʊ). Its new unit is Siemens. The word ‘Admittance’ was initially used by an English engineer, physicist & mathematician Oliver Heaviside in 1887.

Admittance Methodology:

Conductance G=g1+g2+g3+

Susceptance B=(-b1)+(-b2)+ b3

[Admittance] Y =( G2+B2)

Current I =VY ; Power factors cosΦ=g/y

Triangle of Admittance:

The admittance triangle is represented in the same way as the impedance triangle. Subsequently, the impedance (Z) of the circuit has two rectangular components, resistance (R) & reactance (X). Similarly, the [Admittance] (Y) also has two features: conductance (g) and Susceptance (b).


The base of the [Admittance] triangle is known as conductance. Moreover, the conductance value is always positive regardless of the circuit parameters.


The perpendicular of the [Admittance] triangle is called Susceptance. It is a positive value for capacitive reactance & it is a negative value for inductive reactance.

Examples of Admittance Uses in Circuit Analysis:

Here are some examples of how Admittance is used in circuit analysis and design:

  • [Admittance] can be used to calculate the current that will flow through a circuit when a voltage is applied to it.
  • [Admittance] can be used to design circuits to have a specific input or output impedance.
  • [Admittance] can be used to design filters that allow or block specific current frequencies.
  • [Admittance] can be used to design matching circuits that maximize the power transfer between two circuits.


In conclusion, [Admittance] (Y) measures how effortlessly a circuit allows current to flow through it. The reciprocal of impedance (Z) measures how much a circuit clashes with the flow of current. Siemens (S) is the measurement unit for Admittance (Y), the inverse of ohms.

Additionally, [Admittance] is a significant concept in circuit analysis & design and can be used to calculate a circuit’s current, voltage & power. It can also come in handy to design circuits to have specific electrical characteristics.

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