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
120 Vload22.5 kW, 6 kvarI = ?

A single-phase load connected to a 120 V supply takes 22.5 kW and 6 kvar. Find the current I drawn from the supply.

V = 120 VP = 22.5 kWQ = 6 kvar
I = A
2.Easy
240 Vload10.5 kW, 8 kvarI = ?

A single-phase load connected to a 240 V supply takes 10.5 kW and 8 kvar. Find the current I drawn from the supply.

V = 240 VP = 10.5 kWQ = 8 kvar
I = A
3.Medium
120 VZ5 + j12 ΩI

A load with impedance Z = 5 + j12 Ω is connected to a 120 V (rms) single-phase supply. Find the real power P it absorbs.

V = 120 VZ = 5 + j12 Ω
P = W
4.Medium
P = 10 kWQ = ?Sφ

A single-phase motor takes 10 kW at a power factor of 0.75 lagging from a 240 V supply. Find the reactive power Q it draws.

P = 10 kWpf = 0.75V = 240 V
Q = kvar
5.Hard
P = 45 kWQ1​S1​φ1​QC​

A single-phase load takes 45 kW at a power factor of 0.65 lagging from a 230 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the capacitance C needed.

P = 45 kWpf1 = 0.65pf2 = 0.95V = 230 Vf = 50 Hz
C = µF
6.Hard
P = 45 kWQ1​S1​φ1​QC​

A single-phase load takes 45 kW at a power factor of 0.7 lagging from a 240 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the new line current Inew.

P = 45 kWpf1 = 0.7pf2 = 0.98V = 240 Vf = 50 Hz
Inew = A

Answer key

  1. 1. I = 194.1 A
  2. 2. I = 55 A
  3. 3. P = 426 W
  4. 4. Q = 8.819 kvar
  5. 5. C = 2276 µF
  6. 6. Inew = 191.3 A

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