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 10 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 = 10 Apf = cos φ = 0.65
P = W
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 16 A (rms) from a 230 V (rms) supply at a power factor of 0.6 lagging. Find the real power P it takes.

V = 230 VI = 16 Apf = cos φ = 0.6
P = W
3.Medium
P = 31 kWQSφ

A single-phase motor takes 31 kW at a power factor of 0.9 lagging from a 400 V supply. Find the line current I.

P = 31 kWpf = 0.9V = 400 V
I = A
4.Medium
120 VZ3 + j4 ΩI

A load with impedance Z = 3 + j4 Ω is connected to a 120 V (rms) single-phase supply. Find the apparent power S.

V = 120 VZ = 3 + j4 Ω
S = VA
5.Hard
P = 5 kWQ1​S1​φ1​QC​

A single-phase load takes 5 kW at a power factor of 0.7 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the new line current Inew.

P = 5 kWpf1 = 0.7pf2 = 0.98V = 240 Vf = 60 Hz
Inew = A
6.Hard
P = 40 kWQ1​S1​φ1​QC​

A single-phase load takes 40 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 = 40 kWpf1 = 0.6pf2 = 0.95V = 240 Vf = 60 Hz
Inew = A

Answer key

  1. 1. P = 1495 W
  2. 2. P = 2208 W
  3. 3. I = 86.11 A
  4. 4. S = 2880 VA
  5. 5. Inew = 21.26 A
  6. 6. Inew = 175.4 A

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