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
N1​ = 960N2​ = ?960 V120 V

An ideal transformer must step 960 V down to 120 V. Its primary winding has 960 turns. How many turns N2 does the secondary winding need?

V1 = 960 VV2 = 120 VN1 = 960
N2 =
2.Easy
N1​ = 320N2​ = ?960 V120 V

An ideal transformer must step 960 V down to 120 V. Its primary winding has 320 turns. How many turns N2 does the secondary winding need?

V1 = 960 VV2 = 120 VN1 = 320
N2 =
3.Medium
2 ΩN1​N2​18 Ω

An amplifier with an output resistance of 18 Ω drives a 2 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 18 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

Rs = 18 ΩRL = 2 Ω
a =
4.Medium
RL​ = 4 Ω41960 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 960 V applied to its primary winding. A 4 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 4:1V1 = 960 VRL = 4 Ω
I1 = A
5.Hard
200 kVA

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 Sη,max, in kVA, is its efficiency highest?

S = 200 kVAPcore = 1600 WPcu,fl = 4000 W
Sη,max = kVA
6.Hard
200 kVA

A single-phase 200 kVA transformer has a core loss of 1200 W and a copper loss of 1800 W at rated load. At what load Sη,max, in kVA, is its efficiency highest?

S = 200 kVAPcore = 1200 WPcu,fl = 1800 W
Sη,max = kVA

Answer key

  1. 1. N2 = 120
  2. 2. N2 = 40
  3. 3. a = 3
  4. 4. I1 = 15 A
  5. 5. Sη,max = 126.5 kVA
  6. 6. Sη,max = 163.3 kVA

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