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 14 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 = 14 Apf = cos φ = 0.85

P = W

2.Easy

A load takes 43 kW of real power and 15.5 kvar of reactive power (lagging). Find the apparent power S.

P = 43 kWQ = 15.5 kvar

S = kVA

3.Medium

A single-phase motor takes 36 kW at a power factor of 0.75 lagging from a 400 V supply. Find the line current I.

P = 36 kWpf = 0.75V = 400 V

I = A

4.Medium

Two loads are connected in parallel to a 240 V single-phase supply: a 9 kW load at a power factor of 0.8 lagging and a 4 kW heater (unity power factor). Find the total current I drawn from the supply.

V = 240 VP₁ = 9 kW, pf₁ = 0.8 laggingP₂ = 4 kW, pf₂ = 1

I = A

5.Hard

A single-phase load takes 35 kW at a power factor of 0.65 lagging from a 230 V, 60 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the capacitance C needed.

P = 35 kWpf₁ = 0.65pf₂ = 0.98V = 230 Vf = 60 Hz

C = µF

6.Hard

A single-phase load takes 21 kW at a power factor of 0.8 lagging from a 240 V, 50 Hz supply. A 470 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 21 kWpf₁ = 0.8V = 240 Vf = 50 HzC = 470 µF

I = A

Answer key

1. P = 2856 W
2. S = 45.71 kVA
3. I = 120 A
4. I = 61.03 A
5. C = 1695 µF
6. I = 92.56 A

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