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 VloadP = 1656 W8 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 8 A and 1656 W. Find the power factor cos φ of the load.

V = 230 VI = 8 AP = 1656 W
cos φ =
2.Easy
240 VloadP = 2520 W17.5 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 17.5 A and 2520 W. Find the power factor cos φ of the load.

V = 240 VI = 17.5 AP = 2520 W
cos φ =
3.Medium
230 VR + jXP = 2484 W13.5 A

An inductive load takes 13.5 A and 2484 W from a 230 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find R.

V = 230 VI = 13.5 AP = 2484 W
R = Ω
4.Medium
240 VZ9 + j12 ΩI

A load with impedance Z = 9 + j12 Ω is connected to a 240 V (rms) single-phase supply. Find the reactive power Q it absorbs.

V = 240 VZ = 9 + j12 Ω
Q = var
5.Hard
P = 40 kWQ1​S1​φ1​QC​

A single-phase load takes 40 kW at a power factor of 0.7 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 = 40 kWpf1 = 0.7pf2 = 0.92V = 240 Vf = 60 Hz
QC = kvar
6.Hard
P1​ = 61 kWQ1​S1​φ

A 200 kVA single-phase transformer supplies a load of 61 kW at a power factor of 0.65 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 = 200 kVAP1 = 61 kWpf1 = 0.65
ΔP = kW

Answer key

  1. 1. cos φ = 0.9
  2. 2. cos φ = 0.6
  3. 3. R = 13.63 Ω
  4. 4. Q = 3072 var
  5. 5. QC = 23.77 kvar
  6. 6. ΔP = 125.9 kW

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