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What is Admittance?

The reciprocal of impedance, Y = 1/Z [S]. With the conductance G as the real part and the susceptance B as the imaginary part, it is written Y = G + jB. In a parallel circuit the admittances of the elements simply add, so a parallel RLC circuit is written simply as Y = 1/R + j(ωC − 1/(ωL)). For Z = 3 + j4 Ω, Y = 0.12 − j0.16 S; for an inductive load the susceptance is negative.

Japanese name: アドミタンス

Admittance appears in 4 practice questions across 1 topic, including Circuit Analysis: AC, Linear Circuits and Transients.

Field: Circuit Analysis: AC, Linear Circuits and Transients

Try it: questions about Admittance

Which of the following is the admittance Y of a load whose impedance is Z = 3 + j4 [Ω]?

  1. A0.12 − j0.16 S
  2. B0.12 + j0.16 S
  3. CAbout 0.33 − j0.25 S
Show answer and explanation

Answer: A. 0.12 − j0.16 S

Method 1 (rationalizing the denominator): multiplying the numerator and denominator of Y = 1/(3 + j4) by the complex conjugate 3 − j4 gives Y = (3 − j4)/(3² + 4²) = (3 − j4)/25 = 0.12 − j0.16 S. Method 2 (polar form): |Z| = √(3² + 4²) = 5 Ω and the angle is about 53.1°, so Y = (1/5)∠−53.1° = 0.2∠−53.1° S, which in rectangular form is the same 0.12 − j0.16 S. When the impedance is inductive (positive imaginary part), the imaginary part of the admittance (the susceptance) is negative.

Admittance in the explanations

Questions that mention Admittance (4)

  1. Which of the following is the admittance Y of a load whose impedance is Z = 3 + j4 [Ω]?
  2. In the parallel RLC circuit in the figure, the source frequency is set to the resonant frequency f0 = 1/(2π√(LC)). Which of the following correctly describes the circuit?
  3. In the parallel RLC circuit in the figure, R = 20 kΩ, L = 1 mH and C = 10 nF. Near the resonant frequency, which of the following is closest to the difference between the two frequencies at which the magnitude of the circuit impedance falls to 1/√2 of its value at resonance (the bandwidth)?
  4. Which of the following is the s-domain impedance Z(s) of a resistor R and a capacitor C connected in parallel?

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Related terms

Impedance Resonant circuit Phasor Q factor (quality factor) Mesh analysis Nodal analysis Norton's theorem Partial fraction decomposition Reactance Reactive power

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