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.

New worksheet Practise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________ Date: ____________

1.Easy

An ideal transformer has 500 turns on its primary winding and 25 turns on its secondary winding. The primary is connected to a 4800 V AC supply. Find the secondary voltage V₂.

N₁ = 500N₂ = 25V₁ = 4800 V

V₂ = V

2.Easy

An ideal transformer has 200 turns on its primary winding and 1000 turns on its secondary winding. The primary is connected to a 690 V AC supply. Find the secondary voltage V₂.

N₁ = 200N₂ = 1000V₁ = 690 V

V₂ = V

3.Medium

An amplifier with an output resistance of 16 Ω drives a 4 Ω loudspeaker through an ideal transformer. For maximum power transfer the loudspeaker must look like 16 Ω from the amplifier. Find the turns ratio a = N₁/N₂.

R_s = 16 ΩR_L = 4 Ω

a =

4.Medium

A single-phase 75 kVA, 2400/240 V transformer operates at its rated load. Treat it as ideal. Find the current I_HV in the high-voltage winding.

S = 75 kVAV₁ = 2400 VV₂ = 240 V

I_HV = A

5.Hard

A single-phase 50 kVA transformer has a core loss of 400 W and a copper loss of 800 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 50 kVAP_core = 400 WP_cu,fl = 800 W

S_η,max = kVA

6.Hard

A single-phase 250 kVA transformer has a core loss of 750 W and a copper loss of 3000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 250 kVAP_core = 750 WP_cu,fl = 3000 W

S_η,max = kVA

Answer key

1. V₂ = 240 V
2. V₂ = 3450 V
3. a = 2
4. I_HV = 31.25 A
5. S_η,max = 35.36 kVA
6. S_η,max = 125 kVA

Full step-by-step solutions: practise this topic on examproblems.com.