Transformers(Electrical Engineering ) Questions and Answers

Question 1. Insertion of resistance in the rotcir of an induction motor to develop a given torque
  1.    decreases the rotor current
  2.    increases the rotor current
  3.    rotor current becomes zero
  4.    rotor current rernains same
Explanation:-
Answer: Option D. -> rotor current rernains same
Question 2. The efficiency of a transformer will be maximum when
  1.    copper losses = hysteresis losses
  2.    hysteresis losses = eddy current losses
  3.    eddy current losses = copper losses
  4.    copper losses = iron losses
Explanation:-
Answer: Option D. -> copper losses = iron losses
Question 3. Which of the following protection is normally not provided on small distribution transformers?
  1.    Overfluxing protection
  2.    Buchholz relay
  3.    Overcurrent protection
  4.    All of the above
Explanation:-
Answer: Option B. -> Buchholz relay
Question 4. The maximum efficiency of a distribution transformer is
  1.    at no load
  2.    at 50% full load
  3.    at 80% full load
  4.    at full load
Explanation:-
Answer: Option B. -> at 50% full load
Question 5. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect?
  1.    Its secondary current is 5 A
  2.    Its secondary voltage is 400 V
  3.    Its rating is 2 kVA
  4.    Its secondary current is 20 A
Explanation:-
Answer: Option D. -> Its secondary current is 20 A
Question 6. Greater the secondary leakage flux
  1.    less will be the secondary induced e.m.f.
  2.    less will be the primary induced e.m.f.
  3.    less will be the primary terminal voltage
  4.    none of the above
Explanation:-
Answer: Option A. -> less will be the secondary induced e.m.f.
Question 7. Buchholz's relay gives warning and protection against
  1.    electrical fault inside the transformer itself
  2.    electrical fault outside the transformer in outgoing feeder
  3.    for both outside and inside faults
  4.    none of the above
Explanation:-
Answer: Option A. -> electrical fault inside the transformer itself
Question 8. The transformer laminations are insulated from each other by
  1.    mica strip
  2.    thin coat of varnish
  3.    paper
  4.    any of the above
Explanation:-
Answer: Option B. -> thin coat of varnish
Question 9. In the transformer following winding has got more cross-sectional area
  1.    Low voltage winding
  2.    High voltage winding
  3.    Primary winding
  4.    Secondary winding
Explanation:-
Answer: Option A. -> Low voltage winding
Question 10. A transformer core is laminated to
  1.    reduce hysteresis loss
  2.    reduce eddy current losses
  3.    reduce copper losses
  4.    reduce all above losses
Explanation:-
Answer: Option B. -> reduce eddy current losses
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