Transformers worksheet with answers

Free printable Transformers 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

An ideal transformer has 120 turns on its primary winding and 1200 turns on its secondary winding. The primary is connected to a 230 V AC supply. Find the secondary voltage V₂.

N₁ = 120N₂ = 1200V₁ = 230 V

V₂ = V

2.Easy

An ideal transformer has 150 turns on its primary winding and 1500 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V₂.

N₁ = 150N₂ = 1500V₁ = 240 V

V₂ = V

3.Medium

An amplifier with an output resistance of 1024 Ω drives a 16 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 1024 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 1024 ΩR_L = 16 Ω

a =

4.Medium

A 16 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 3:1. Find the resistance R_1′ seen looking into the primary winding.

N₁:N₂ = 3:1R_L = 16 Ω

R_1′ = Ω

5.Hard

A single-phase 100 kVA transformer has a core loss of 800 W. At rated load and a power factor of 0.95 lagging its efficiency is 97%. Find the full-load copper loss P_cu,fl in watts.

S = 100 kVAP_core = 800 Wpf = 0.95η = 97%

P_cu,fl = W

6.Hard

A single-phase 500 kVA transformer has a core loss of 2000 W. At rated load and a power factor of 0.9 lagging its efficiency is 97.5%. Find the full-load copper loss P_cu,fl in watts.

S = 500 kVAP_core = 2000 Wpf = 0.9η = 97.5%

P_cu,fl = W

Answer key

1. V₂ = 2300 V
2. V₂ = 2400 V
3. a = 8
4. R_1′ = 144 Ω
5. P_cu,fl = 2138 W
6. P_cu,fl = 9538 W

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