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.

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1.Easy
240 Vload27.5 kW, 24 kvarI = ?

A single-phase load connected to a 240 V supply takes 27.5 kW and 24 kvar. Find the current I drawn from the supply.

V = 240 VP = 27.5 kWQ = 24 kvar
I = A
2.Easy
230 VloadP = 2576 W14 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 230 V, 14 A and 2576 W. Find the reactive power Q taken by the load.

V = 230 VI = 14 AP = 2576 W
Q = var
3.Medium
P = 11 kWQSφ

A single-phase motor takes 11 kW at a power factor of 0.85 lagging from a 240 V supply. Find the line current I.

P = 11 kWpf = 0.85V = 240 V
I = A
4.Medium
400 V125 kW, 0.624 kW, 0.9I = ?

Two loads are connected in parallel to a 400 V single-phase supply: a 25 kW load at a power factor of 0.6 lagging and a 4 kW load at a power factor of 0.9 leading. Find the total current I drawn from the supply.

V = 400 VP1 = 25 kW, pf1 = 0.6 laggingP2 = 4 kW, pf2 = 0.9 leading
I = A
5.Hard
240 V50 Hzload19 kW, 0.6C220 µFI = ?

A single-phase load takes 19 kW at a power factor of 0.6 lagging from a 240 V, 50 Hz supply. A 220 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 19 kWpf1 = 0.6V = 240 Vf = 50 HzC = 220 µF
I = A
6.Hard
100 V60 HzRs​ = 50 ΩXs​ = j3 ΩZL​ = ?

A 100 V (rms), 60 Hz source has an internal impedance Zs = 50 + j3 Ω. The load impedance ZL can be chosen freely. Find the maximum real power Pmax that can be delivered to the load.

Vs = 100 V (rms)f = 60 HzZs = 50 + j3 Ω
Pmax = W

Answer key

  1. 1. I = 152.1 A
  2. 2. Q = 1932 var
  3. 3. I = 53.92 A
  4. 4. I = 106.9 A
  5. 5. I = 119.1 A
  6. 6. Pmax = 50 W

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