AC power & power factor worksheet with answers

Free printable AC power & power factor 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
PQ = ?S = V·Iφ

A single-phase load draws 5 A (rms) from a 120 V (rms) supply at a power factor of 0.85 lagging. Find the reactive power Q it takes.

V = 120 VI = 5 Apf = cos φ = 0.85
Q = var
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 11 A (rms) from a 230 V (rms) supply at a power factor of 0.9 lagging. Find the real power P it takes.

V = 230 VI = 11 Apf = cos φ = 0.9
P = W
3.Medium
230 VR + jXP = 2576 W14 A

An inductive load takes 14 A and 2576 W from a 230 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find X.

V = 230 VI = 14 AP = 2576 W
X = Ω
4.Medium
P = 9 kWQ = ?Sφ

A single-phase motor takes 9 kW at a power factor of 0.6 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 9 kWpf = 0.6V = 230 V
Q = kvar
5.Hard
400 V60 Hzload22 kW, 0.7C47 µFI = ?

A single-phase load takes 22 kW at a power factor of 0.7 lagging from a 400 V, 60 Hz supply. A 47 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 22 kWpf1 = 0.7V = 400 Vf = 60 HzC = 47 µF
I = A
6.Hard
230 V60 Hzload16 kW, 0.8C470 µFI = ?

A single-phase load takes 16 kW at a power factor of 0.8 lagging from a 230 V, 60 Hz supply. A 470 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 16 kWpf1 = 0.8V = 230 Vf = 60 HzC = 470 µF
I = A

Answer key

  1. 1. Q = 316.1 var
  2. 2. P = 2277 W
  3. 3. X = 9.857 Ω
  4. 4. Q = 12 kvar
  5. 5. I = 73.68 A
  6. 6. I = 70.5 A

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