AC impedance & phasors worksheet with answers

Free printable AC impedance & phasors worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
100 V60 HzR = 10 ΩL = 150 mH

A series RL circuit is connected to a 100 V (rms), 60 Hz supply. Find the rms voltage VL across the inductor.

V = 100 V (rms)f = 60 HzR = 10 ΩL = 150 mH
VL = V
2.Easy
120 V50 HzR = 50 ΩL = 250 mHI

A series RL circuit is connected to a 120 V (rms), 50 Hz supply. Find the rms current I.

V = 120 V (rms)f = 50 HzR = 50 ΩL = 250 mH
I = A
3.Medium
120 V500 HzR = 100 ΩL = 50 mHC = 22 µFI

A series RLC circuit is connected to a 120 V (rms), 500 Hz supply. Find the power factor cos φ of the circuit.

V = 120 V (rms)f = 500 HzR = 100 ΩL = 50 mHC = 22 µF
cos φ =
4.Medium
Vf0​ = 50 HzRL = 20 mHC = ?

A series RLC circuit with L = 20 mH must resonate at 50 Hz. Find the capacitance C needed.

f0 = 50 HzL = 20 mH
C = µF
5.Hard
5 Vf0​R = 50 ΩL = 50 mHC = 0.22 µF

A series RLC circuit is driven by a 5 V (rms) source whose frequency is set to the resonant frequency of the circuit. Find the rms voltage VL across the inductor.

V = 5 V (rms)R = 50 ΩL = 50 mHC = 0.22 µF
VL = V
6.Hard
24 V100 HzR = 30 ΩL = 100 mHC = 22 µF

A series RLC circuit is connected to a 24 V (rms), 100 Hz supply. Find the resonant frequency f0 of the circuit.

V = 24 V (rms)f = 100 HzR = 30 ΩL = 100 mHC = 22 µF
f0 = Hz

Answer key

  1. 1. VL = 98.47 V
  2. 2. I = 1.289 A
  3. 3. cos φ = 0.5741
  4. 4. C = 506.6 µF
  5. 5. VL = 47.67 V
  6. 6. f0 = 107.3 Hz

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