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 60 turns on its primary winding and 120 turns on its secondary winding. The primary is connected to a 110 V AC supply. Find the secondary voltage V₂.

N₁ = 60N₂ = 120V₁ = 110 V

V₂ = V

2.Easy

An ideal transformer has 250 turns on its primary winding and 25 turns on its secondary winding. The primary is connected to a 2400 V AC supply. Find the secondary voltage V₂.

N₁ = 250N₂ = 25V₁ = 2400 V

V₂ = V

3.Medium

An ideal transformer with a turns ratio N₁:N₂ = 2:1 has 240 V applied to its primary winding. A 48 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 2:1V₁ = 240 VR_L = 48 Ω

I₁ = A

4.Medium

An ideal transformer with a turns ratio N₁:N₂ = 4:1 has 480 V applied to its primary winding. An 8 Ω resistor is connected across the secondary winding. Find the primary current I₁.

N₁:N₂ = 4:1V₁ = 480 VR_L = 8 Ω

I₁ = A

5.Hard

A single-phase 150 kVA transformer has a core loss of 600 W. At rated load and a power factor of 0.95 lagging its efficiency is 96.5%. Find the full-load copper loss P_cu,fl in watts.

S = 150 kVAP_core = 600 Wpf = 0.95η = 96.5%

P_cu,fl = W

6.Hard

A single-phase 200 kVA transformer has a core loss of 1200 W and a copper loss of 3000 W at rated load. At what load S_η,max, in kVA, is its efficiency highest?

S = 200 kVAP_core = 1200 WP_cu,fl = 3000 W

S_η,max = kVA

Answer key

1. V₂ = 220 V
2. V₂ = 240 V
3. I₁ = 1.25 A
4. I₁ = 3.75 A
5. P_cu,fl = 4568 W
6. S_η,max = 126.5 kVA

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