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Impedance & Admittance

Impedance (Z)

Here:

  • : Resistance
  • : Reactance

Admittance (Y)

Inverse of impedance.

Here:

  • : Conductance
  • : Susceptance

From the definitions:

For simple circuit elements

Resistor

Let is applied across a resistor with resistance . From Ohm’s law:

No changes in frequency, phase angle. is in phase with . doesn’t have reactance.

Inductor

Let is applied across an inductor with inductance .

Reactance of the inductor is .

Capacitor

Let is applied across an capacitor with capacitance .

Reactance of the capacitor (capacitive reactance) is .

For complex circuit elements

For a series circuit

Resultant impedance is the sum of each component’s impedance.

For a parallel circuit

Resultant admittance is the sum of each component’s admittance.