Questions and answers for exam Preparation

MCQs

Total Questions : 631 | Page 8 of 64 pages

Question 71. The purpose of providing an iron core in a transformer is to

provide support to windings
reduce hysteresis loss
decrease the reluctance of the magnetic path
reduce eddy current losses

Discuss Question

Answer: Option C. -> decrease the reluctance of the magnetic path

Question 72. A good voltage regulation of a transformer means

output voltage fluctuation from no load to full load is least
output voltage fluctuation with power factor is least
difference between primary and secondary voltage is least
difference between primary and secondary voltage is maximum

Discuss Question

Answer: Option A. -> output voltage fluctuation from no load to full load is least

Question 73. A Buchholz relay can be installed on

auto-transformers
air-cooled transformers
welding transformers
oil cooled transformers

Discuss Question

Answer: Option D. -> oil cooled transformers

Question 74. If the percentage impedances of the two transformers working in parallel are different, then

transformers will be overheated
power factors of both the transformers will be same
parallel operation will be not possible
parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

Discuss Question

Answer: Option D. -> parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

Question 75. An ideal transformer will have maximum efficiency at a load such that

copper loss = iron loss
copper loss < iron loss
copper loss > iron loss
none of the above

Discuss Question

Answer: Option A. -> copper loss = iron loss

Question 76. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be

6400 W
1600 W
800 W
400 W

Discuss Question

Answer: Option D. -> 400 W

Question 77. The size of a transformer core will depend on

frequency
area of the core
flux density of the core material
(A) and (B) both

Discuss Question

Answer: Option D. -> (A) and (B) both

Question 78. A transformer cannot raise or lower the voltage of a D.C. supply because

There is no need to change the D.C. voltage
A D.C. circuit has more losses
Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero
None of the above

Discuss Question

Answer: Option C. -> Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero

Question 79. Which of the following loss in a transformer is zero even at full load ?