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 = 23 kWQ = 14 kvarSφ

A load takes 23 kW of real power and 14 kvar of reactive power (lagging). Find the power factor cos φ.

P = 23 kWQ = 14 kvar
cos φ =
2.Easy
P = ?QS = V·Iφ

A single-phase load draws 18 A (rms) from a 120 V (rms) supply at a power factor of 0.75 lagging. Find the real power P it takes.

V = 120 VI = 18 Apf = cos φ = 0.75
P = W
3.Medium
P = 15 kWQ = ?Sφ

A single-phase motor takes 15 kW at a power factor of 0.9 lagging from a 230 V supply. Find the reactive power Q it draws.

P = 15 kWpf = 0.9V = 230 V
Q = kvar
4.Medium
P = 33 kWQSφ

A single-phase motor takes 33 kW at a power factor of 0.8 lagging from a 400 V supply. Find the line current I.

P = 33 kWpf = 0.8V = 400 V
I = A
5.Hard
P = 25 kWQ1​S1​φ1​QC​

A single-phase load takes 25 kW at a power factor of 0.6 lagging from a 230 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.95. Find the new line current Inew.

P = 25 kWpf1 = 0.6pf2 = 0.95V = 230 Vf = 60 Hz
Inew = A
6.Hard
P = 45 kWQ1​S1​φ1​QC​

A single-phase load takes 45 kW at a power factor of 0.65 lagging from a 240 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the reactive power QC the capacitor must supply.

P = 45 kWpf1 = 0.65pf2 = 0.92V = 240 Vf = 60 Hz
QC = kvar

Answer key

  1. 1. cos φ = 0.8542
  2. 2. P = 1620 W
  3. 3. Q = 7.265 kvar
  4. 4. I = 103.1 A
  5. 5. Inew = 114.4 A
  6. 6. QC = 33.44 kvar

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