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
P = 34.5 kWQ = 14.5 kvarS = ?φ

A load takes 34.5 kW of real power and 14.5 kvar of reactive power (lagging). Find the apparent power S.

P = 34.5 kWQ = 14.5 kvar
S = kVA
2.Easy
120 Vload26 kW, 5.5 kvarI = ?

A single-phase load connected to a 120 V supply takes 26 kW and 5.5 kvar. Find the current I drawn from the supply.

V = 120 VP = 26 kWQ = 5.5 kvar
I = A
3.Medium
P = 28 kWQ = ?Sφ

A single-phase motor takes 28 kW at a power factor of 0.6 lagging from a 240 V supply. Find the reactive power Q it draws.

P = 28 kWpf = 0.6V = 240 V
Q = kvar
4.Medium
120 VR + jXP = 1152 W16 A

An inductive load takes 16 A and 1152 W from a 120 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find R.

V = 120 VI = 16 AP = 1152 W
R = Ω
5.Hard
P = 20 kWQ1​S1​φ1​QC​

A single-phase load takes 20 kW at a power factor of 0.65 lagging from a 400 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.9. Find the capacitance C needed.

P = 20 kWpf1 = 0.65pf2 = 0.9V = 400 Vf = 60 Hz
C = µF
6.Hard
P = 25 kWQ1​S1​φ1​QC​

A single-phase load takes 25 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 0.98. Find the new line current Inew.

P = 25 kWpf1 = 0.6pf2 = 0.98V = 240 Vf = 60 Hz
Inew = A

Answer key

  1. 1. S = 37.42 kVA
  2. 2. I = 221.5 A
  3. 3. Q = 37.33 kvar
  4. 4. R = 4.5 Ω
  5. 5. C = 227.1 µF
  6. 6. Inew = 106.3 A

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