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, 19.5 A and 3042 W. Find the power factor cos φ of the load.

V = 240 VI = 19.5 AP = 3042 W

cos φ =

2.Easy

A voltmeter, an ammeter and a wattmeter connected to a single-phase inductive load read 240 V, 13 A and 2184 W. Find the power factor cos φ of the load.

V = 240 VI = 13 AP = 2184 W

cos φ =

3.Medium

An inductive load takes 4.5 A and 324 W from a 120 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find R.

V = 120 VI = 4.5 AP = 324 W

R = Ω

4.Medium

An inductive load takes 12 A and 1224 W from a 120 V (rms) single-phase supply. Model it as a resistance R in series with a reactance X. Find X.

V = 120 VI = 12 AP = 1224 W

X = Ω

5.Hard

A single-phase load takes 5 kW at a power factor of 0.75 lagging from a 230 V, 50 Hz supply. A capacitor connected in parallel raises the power factor to 0.92. Find the new line current I_new.

P = 5 kWpf₁ = 0.75pf₂ = 0.92V = 230 Vf = 50 Hz

I_new = A

6.Hard

A single-phase load takes 45 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 0.92. Find the capacitance C needed.

P = 45 kWpf₁ = 0.65pf₂ = 0.92V = 230 Vf = 60 Hz

C = µF

Answer key

1. cos φ = 0.65
2. cos φ = 0.7
3. R = 16 Ω
4. X = 5.268 Ω
5. I_new = 23.63 A
6. C = 1677 µF

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