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 VloadP = 1482 W9.5 A

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 9.5 A and 1482 W. Find the reactive power Q taken by the load.

V = 240 VI = 9.5 AP = 1482 W
Q = var
2.Easy
P = 35.5 kWQ = 44 kvarSφ

A load takes 35.5 kW of real power and 44 kvar of reactive power (lagging). Find the power factor cos φ.

P = 35.5 kWQ = 44 kvar
cos φ =
3.Medium
P = 40 kWQ = ?Sφ

A single-phase motor takes 40 kW at a power factor of 0.9 lagging from a 400 V supply. Find the reactive power Q it draws.

P = 40 kWpf = 0.9V = 400 V
Q = kvar
4.Medium
P = 9 kWQSφ

A single-phase motor takes 9 kW at a power factor of 0.65 lagging from a 240 V supply. Find the line current I.

P = 9 kWpf = 0.65V = 240 V
I = A
5.Hard
P = 15 kWQ1​S1​φ1​QC​

A single-phase load takes 15 kW at a power factor of 0.6 lagging from a 240 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.98. Find the reactive power QC the capacitor must supply.

P = 15 kWpf1 = 0.6pf2 = 0.98V = 240 Vf = 50 Hz
QC = kvar
6.Hard
240 V60 Hzload10 kW, 0.6C220 µFI

A single-phase load takes 10 kW at a power factor of 0.6 lagging from a 240 V, 60 Hz supply. A 220 µF capacitor is connected in parallel with the load. Find the new power factor cos φ seen by the supply.

P = 10 kWpf1 = 0.6V = 240 Vf = 60 HzC = 220 µF
cos φ =

Answer key

  1. 1. Q = 1733 var
  2. 2. cos φ = 0.6279
  3. 3. Q = 19.37 kvar
  4. 4. I = 57.69 A
  5. 5. QC = 16.95 kvar
  6. 6. cos φ = 0.7598

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