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

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 15 A and 2340 W. Find the power factor cos φ of the load.

V = 240 VI = 15 AP = 2340 W

cos φ =

2.Easy

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 6 A and 1080 W. Find the power factor cos φ of the load.

V = 240 VI = 6 AP = 1080 W

cos φ =

3.Medium

An inductive load takes 14.5 A and 2958 W from a 240 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find X.

V = 240 VI = 14.5 AP = 2958 W

X = Ω

4.Medium

An inductive load takes 6 A and 1173 W from a 230 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find X.

V = 230 VI = 6 AP = 1173 W

X = Ω

5.Hard

A 100 V (rms), 60 Hz source has an internal impedance Z_s = 20 + j6 Ω. The load impedance Z_L can be chosen freely. Find the maximum real power P_max that can be delivered to the load.

V_s = 100 V (rms)f = 60 HzZ_s = 20 + j6 Ω

P_max = W

6.Hard

A single-phase load takes 9 kW at a power factor of 0.75 lagging from a 240 V, 60 Hz supply. A 47 µF capacitor is connected in parallel with the load. Find the new line current I.

P = 9 kWpf₁ = 0.75V = 240 Vf = 60 HzC = 47 µF

I = A

Answer key

1. cos φ = 0.65
2. cos φ = 0.75
3. X = 8.719 Ω
4. X = 20.19 Ω
5. P_max = 125 W
6. I = 47.29 A

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