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
240 Vload16.5 kW, 16 kvarI = ?

A single-phase load connected to a 240 V supply takes 16.5 kW and 16 kvar. Find the current I drawn from the supply.

V = 240 VP = 16.5 kWQ = 16 kvar
I = A
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 20 A (rms) from a 240 V (rms) supply at a power factor of 0.85 lagging. Find the real power P it takes.

V = 240 VI = 20 Apf = cos φ = 0.85
P = W
3.Medium
P = 19 kWQSφ

A single-phase motor takes 19 kW at a power factor of 0.9 lagging from a 400 V supply. Find the line current I.

P = 19 kWpf = 0.9V = 400 V
I = A
4.Medium
240 VZ6 + j8 ΩI

A load with impedance Z = 6 + j8 Ω is connected to a 240 V (rms) single-phase supply. Find the apparent power S.

V = 240 VZ = 6 + j8 Ω
S = VA
5.Hard
10 V1000 HzRs​ = 10 ΩXs​ = j10 ΩZL​ = ?

A 10 V (rms), 1000 Hz source has an internal impedance Zs = 10 + j10 Ω. The load impedance ZL can be chosen freely. Find the maximum real power Pmax that can be delivered to the load.

Vs = 10 V (rms)f = 1000 HzZs = 10 + j10 Ω
Pmax = W
6.Hard
230 V50 Hzload9 kW, 0.6C100 µFI

A single-phase load takes 9 kW at a power factor of 0.6 lagging from a 230 V, 50 Hz supply. A 100 µF capacitor is connected in parallel with the load. Find the new power factor cos φ seen by the supply.

P = 9 kWpf1 = 0.6V = 230 Vf = 50 HzC = 100 µF
cos φ =

Answer key

  1. 1. I = 95.77 A
  2. 2. P = 4080 W
  3. 3. I = 52.78 A
  4. 4. S = 5760 VA
  5. 5. Pmax = 2.5 W
  6. 6. cos φ = 0.6566

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