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.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
230 Vload24.5 kW, 9 kvarI = ?

A single-phase load connected to a 230 V supply takes 24.5 kW and 9 kvar. Find the current I drawn from the supply.

V = 230 VP = 24.5 kWQ = 9 kvar
I = A
2.Easy
230 VloadP = 1863 W13.5 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 13.5 A and 1863 W. Find the power factor cos φ of the load.

V = 230 VI = 13.5 AP = 1863 W
cos φ =
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 real power P it absorbs.

V = 120 VZ = 12 + j16 Ω
P = W
4.Medium
P = 17 kWQSφ

A single-phase motor takes 17 kW at a power factor of 0.65 lagging from a 230 V supply. Find the line current I.

P = 17 kWpf = 0.65V = 230 V
I = A
5.Hard
P1​ = 75 kWQ1​S1​φ

A 150 kVA single-phase transformer supplies a load of 75 kW at a power factor of 0.85 lagging. How much extra real power ΔP can be added as a resistive (unity power factor) load before the transformer reaches its kVA rating?

Smax = 150 kVAP1 = 75 kWpf1 = 0.85
ΔP = kW
6.Hard
P = 20 kWQ1​S1​φ1​QC​

A single-phase load takes 20 kW at a power factor of 0.7 lagging from a 400 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the capacitance C needed.

P = 20 kWpf1 = 0.7pf2 = 0.95V = 400 Vf = 60 Hz
C = µF

Answer key

  1. 1. I = 113.5 A
  2. 2. cos φ = 0.6
  3. 3. P = 432 W
  4. 4. I = 113.7 A
  5. 5. ΔP = 67.62 kW
  6. 6. C = 229.3 µF

Full step-by-step solutions: practise this topic on examproblems.com.