Admittance (Y) is a fundamental concept in the field of electrical engineering and A.C. (alternating current) circuit analysis. It is the reciprocal of impedance (Z) and is used to describe the ease with which alternating current flows through an electrical circuit.
The admittance (Y) of an electrical element or a circuit is given by the formula:
=
1
Y=
Z
1
where:
Y represents the admittance in siemens (S)
Z represents the impedance in ohms (
Ω
Ω)
Impedance (
Z) combines both resistance (
R) and reactance (
X) in a complex manner and is a measure of opposition to the flow of alternating current in a circuit. It can be expressed in rectangular form as:
=
+
Z=R+jX
where:
R is the resistance in ohms (
Ω
Ω)
j is the imaginary unit (
=
−
1
j=
−1
)
X is the reactance in ohms (
Ω
Ω)
Reactance can be inductive (
X
L
) or capacitive (
X
C
), depending on the nature of the circuit element. Inductive reactance is associated with coils and transformers, while capacitive reactance is associated with capacitors.
The admittance can also be expressed in rectangular form, similar to impedance:
=
+
Y=G+jB
where:
G is the conductance in siemens (S)
j is the imaginary unit (
=
−
1
j=
−1
)
B is the susceptance in siemens (S)
Just as resistance is a measure of how easily direct current flows through a circuit, conductance (
G) is a measure of how easily alternating current flows through a circuit. Susceptance (
B) is the analog of reactance for admittance and represents the ability of a circuit to store or release energy.
In summary, admittance (
Y) is the reciprocal of impedance (
Z) and is used to quantify how easily alternating current flows through a circuit. It takes into account both conductance (
G) and susceptance (
B) components, which are analogous to resistance and reactance, respectively, in impedance. Admittance is a crucial concept in AC circuit analysis, especially when dealing with complex circuits containing multiple elements with varying conductance and susceptance values.