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 60 turns on its primary winding and 240 turns on its secondary winding. The primary is connected to a 110 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 240V₁ = 110 V

V₂ = V

2.Easy

An ideal transformer must step 2300 V down to 230 V. Its primary winding has 800 turns. How many turns N₂ does the secondary winding need?

V₁ = 2300 VV₂ = 230 VN₁ = 800

N₂ =

3.Medium

An amplifier with an output resistance of 10800 Ω drives a 75 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 10800 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 10800 ΩR_L = 75 Ω

a =

4.Medium

An amplifier with an output resistance of 288 Ω drives an 8 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 288 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 288 ΩR_L = 8 Ω

a =

5.Hard

A single-phase 200 kVA transformer has a core loss of 600 W and a copper loss of 1200 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 600 WP_cu,fl = 1200 W

S_η,max = kVA

6.Hard

A single-phase 200 kVA transformer has a core loss of 1600 W and a copper loss of 4000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 1600 WP_cu,fl = 4000 W

S_η,max = kVA

Answer key

1. V₂ = 440 V
2. N₂ = 80
3. a = 12
4. a = 6
5. S_η,max = 141.4 kVA
6. S_η,max = 126.5 kVA

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