A transformer is an electrical device which steps the ac voltages from one level to another. Being one of most important device in Electrical and Electronics Engineering various exams, jobs interviews, college tests, include transformers. Given below is the list of most important MCQs on transformer.

1. Which of the following correct explains working of a transformer:

  1. AC to DC
  2. DC to AC
  3. AC to AC
  4. DC to DC

Correct answer: 3. AC to AC

Explanation: A transformer is an electrical machine which converts AC voltage at one level to another


2. The winding connected to ac source is:

  1. Primary winding
  2. Secondary winding
  3. Tertiary winding
  4. None of the above

Correct answer: 1. Primary winding

Explanation: The primary winding is the one to which ac input is applied


3. The winding connected to the load is:

  1. Primary winding
  2. Secondary winding
  3. Tertiary winding
  4. None of the above

Correct answer: 2. Secondary winding


4. Eddy current losses are best reduced in transformers by using:

  1. Laminated core
  2. Tertiary winding
  3. Core form construction
  4. All of the above

Correct answer: 1. Laminated core


5. Application of DC supply to transformer:

  1. Will not impact its working
  2. Increase the primary leakage reactance
  3. Will increases losses
  4. Can burn the primary winding

Correct answer: 4. Can burn the primary winding


6. Leakage flux in transformer:

  1. Cause Eddy current losses
  2. Produce self-inductance
  3. Cause hysteresis losses
  4. None of these

Correct answer: 2. Produce self-inductance


7. The secondary of ___________________ should not be open-circuited when the primary is energized:

  1. Potential transformer
  2. Current transformer
  3. Auto-transformer
  4. Booster transformer

Correct answer: 2. Current transformer

Explanation: Doing so will provide every high voltage at output side


8. If Ns/Np = 0.1 and Is = 5 A, the Ip is:

  1. 50 Amps
  2. 5 Amps
  3. 0.5 Amps
  4. 0.02 Amps

Correct answer: 3. 0.5 Amps

Explanation: Np / Ns = Is / Ip

1/0.1 = 5 A / Ip

Ip = 5 * 0.1 = 5 Amps


9. Copper losses in transformer are found using:

  1. Short-circuit test
  2. Open-circuit test
  3. Both of these
  4. None of these

Correct answer: 1. Short circuit test


10. Core losses in transformer are calculated using:

  1. Short-circuit test
  2. Open-circuit test
  3. Both of these
  4. None of these

Correct answer: 2. Open-circuit test