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
P = ?QS = V·Iφ

A single-phase load draws 12 A (rms) from a 230 V (rms) supply at a power factor of 0.65 lagging. Find the real power P it takes.

V = 230 VI = 12 Apf = cos φ = 0.65
P = W
2.Easy
PQ = ?S = V·Iφ

A single-phase load draws 12 A (rms) from a 230 V (rms) supply at a power factor of 0.9 lagging. Find the reactive power Q it takes.

V = 230 VI = 12 Apf = cos φ = 0.9
Q = var
3.Medium
120 VZ12 + j16 ΩI

A load with impedance Z = 12 + j16 Ω is connected to a 120 V (rms) single-phase supply. Find the apparent power S.

V = 120 VZ = 12 + j16 Ω
S = VA
4.Medium
240 VZ12 + j16 ΩI

A load with impedance Z = 12 + j16 Ω is connected to a 240 V (rms) single-phase supply. Find the real power P it absorbs.

V = 240 VZ = 12 + j16 Ω
P = W
5.Hard
P = 20 kWQ1​S1​φ1​QC​

A single-phase load takes 20 kW at a power factor of 0.6 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the new line current Inew.

P = 20 kWpf1 = 0.6pf2 = 0.95V = 240 Vf = 60 Hz
Inew = A
6.Hard
P = 10 kWQ1​S1​φ1​QC​

A single-phase load takes 10 kW at a power factor of 0.7 lagging from a 230 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.9. Find the new line current Inew.

P = 10 kWpf1 = 0.7pf2 = 0.9V = 230 Vf = 60 Hz
Inew = A

Answer key

  1. 1. P = 1794 W
  2. 2. Q = 1203 var
  3. 3. S = 720 VA
  4. 4. P = 1728 W
  5. 5. Inew = 87.72 A
  6. 6. Inew = 48.31 A

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