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​ = 60N2​ = 300120 VV2​ = ?

An ideal transformer has 60 turns on its primary winding and 300 turns on its secondary winding. The primary is connected to a 120 V AC supply. Find the secondary voltage V2.

N1 = 60N2 = 300V1 = 120 V
V2 = V
2.Easy
N1​ = 6000N2​ = ?9200 V230 V

An ideal transformer must step 9200 V down to 230 V. Its primary winding has 6000 turns. How many turns N2 does the secondary winding need?

V1 = 9200 VV2 = 230 VN1 = 6000
N2 =
3.Medium
8 Ω61

An 8 Ω resistor is connected across the secondary winding of an ideal transformer with a turns ratio N₁:N₂ = 6:1. Find the resistance R1′ seen looking into the primary winding.

N1:N2 = 6:1RL = 8 Ω
R1′ = Ω
4.Medium
RL​ = 30 Ω2014800 VV2​I1​ = ?I2​

An ideal transformer with a turns ratio N₁:N₂ = 20:1 has 4800 V applied to its primary winding. A 30 Ω resistor is connected across the secondary winding. Find the primary current I1.

N1:N2 = 20:1V1 = 4800 VRL = 30 Ω
I1 = A
5.Hard
pf 0.8250 kVA, 50% load

A single-phase 250 kVA transformer has a core loss of 2000 W and a copper loss of 4000 W at rated load. It supplies 50% of its rated kVA at a power factor of 0.8 lagging. Find the total losses Ploss in watts at this load.

S = 250 kVAPcore = 2000 WPcu,fl = 4000 Wx = 0.5pf = 0.8
Ploss = W
6.Hard
pf 0.9250 kVA, 75% load

A single-phase 250 kVA transformer has a core loss of 2000 W and a copper loss of 5000 W at rated load. It supplies 75% of its rated kVA at a power factor of 0.9 lagging. Find the total losses Ploss in watts at this load.

S = 250 kVAPcore = 2000 WPcu,fl = 5000 Wx = 0.75pf = 0.9
Ploss = W

Answer key

  1. 1. V2 = 600 V
  2. 2. N2 = 150
  3. 3. R1′ = 288 Ω
  4. 4. I1 = 0.4 A
  5. 5. Ploss = 3000 W
  6. 6. Ploss = 4813 W

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