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 worksheet Practise 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

A single-phase load draws 16 A (rms) from a 240 V (rms) supply at a power factor of 0.6 lagging. Find the real power P it takes.

V = 240 VI = 16 Apf = cos φ = 0.6

P = W

2.Easy

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 13.5 A and 2754 W. Find the reactive power Q taken by the load.

V = 240 VI = 13.5 AP = 2754 W

Q = var

3.Medium

A single-phase motor takes 8 kW at a power factor of 0.6 lagging from a 230 V supply. Find the line current I.

P = 8 kWpf = 0.6V = 230 V

I = A

4.Medium

Two loads are connected in parallel to a 400 V single-phase supply: a 19 kW load at a power factor of 0.7 lagging and a 15 kW load at a power factor of 0.7 leading. Find the overall power factor cos φ seen by the supply.

V = 400 VP₁ = 19 kW, pf₁ = 0.7 laggingP₂ = 15 kW, pf₂ = 0.7 leading

cos φ =

5.Hard

A single-phase load takes 30 kW at a power factor of 0.75 lagging from a 400 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the reactive power Q_C the capacitor must supply.

P = 30 kWpf₁ = 0.75pf₂ = 0.92V = 400 Vf = 60 Hz

Q_C = kvar

6.Hard

A single-phase load takes 10 kW at a power factor of 0.6 lagging from a 400 V, 50 Hz supply. A 100 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 10 kWpf₁ = 0.6V = 400 Vf = 50 HzC = 100 µF

I = A

Answer key

1. P = 2304 W
2. Q = 1707 var
3. I = 57.97 A
4. cos φ = 0.9929
5. Q_C = 13.68 kvar
6. I = 32.5 A

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