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 worksheetPractise 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
N1​ = 200N2​ = 1600240 VV2​ = ?

An ideal transformer has 200 turns on its primary winding and 1600 turns on its secondary winding. The primary is connected to a 240 V AC supply. Find the secondary voltage V2.

N1 = 200N2 = 1600V1 = 240 V
V2 = V
2.Easy
N1​ = 100N2​ = 1000120 VV2​ = ?

An ideal transformer has 100 turns on its primary winding and 1000 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V2.

N1 = 100N2 = 1000V1 = 120 V
V2 = V
3.Medium
RL​ = 10 Ω51600 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 5:1 has 600 V applied to its primary winding. A 10 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 5:1V1 = 600 VRL = 10 Ω
I1 = A
4.Medium
8 Ω21

An 8 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 2:1. Find the resistance R1′ seen looking into the primary winding.

N1:N2 = 2:1RL = 8 Ω
R1′ = Ω
5.Hard
pf 0.8550 kVA, η = 97%

A single-phase 50 kVA transformer has a core loss of 300 W. At rated load and a power factor of 0.85 lagging its efficiency is 97%. Find the full-load copper loss Pcu,fl in watts.

S = 50 kVAPcore = 300 Wpf = 0.85η = 97%
Pcu,fl = W
6.Hard
pf 0.85100 kVA, 25% load

A single-phase 100 kVA transformer has a core loss of 500 W and a copper loss of 750 W at rated load. It supplies 25% of its rated kVA at a power factor of 0.85 lagging. Find the total losses Ploss in watts at this load.

S = 100 kVAPcore = 500 WPcu,fl = 750 Wx = 0.25pf = 0.85
Ploss = W

Answer key

  1. 1. V2 = 1920 V
  2. 2. V2 = 1200 V
  3. 3. I1 = 2.4 A
  4. 4. R1′ = 32 Ω
  5. 5. Pcu,fl = 1014 W
  6. 6. Ploss = 546.9 W

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