transformers MCQs – Page 6

Practise focused transformers questions with marked answers for exam preparation and subject revision.

transformers Mcqs
101. The secondary of a current transformer is always short-circuited under operating conditions because it____________________?
comments icon0

A. protects the primary circuit

B. is safe to human beings

C. none of the above

D. avoids core saturation and high voltage induction
102. A transformer cannot raise or lower the voltage of a D.C. supply because_______________?
comments icon0

A. a D.C. circuit has more losses

B. none of the above

C. Faradays laws of electromagnetic induction are not valid since the rate of change of flux is zero

D. there is no need to change the D.C. voltage

103. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is_________________?
comments icon0
A. approximately equal to one

B. less than one

C. none of the above

D. great than one

104. Which of the following protection is normally not provided on small distribution transformers ?
comments icon0
A. Buchholz relay

B. Overfluxing protection

C. Overcurrent protection

D. All of the above

105. Minimum voltage regulation occurs when the power factor of the load is_____________?
comments icon0
A. leading

B. zero

C. unity

D. lagging

106. Short circuit test on transformers is conducted to determine____________?
comments icon0

A. core losses

B. hysteresis losses

C. eddy current losses

D. copper losses
107. Negative voltage regulation is indicative that the load is___________?
comments icon0
A. capacitive only

B. none of the above

C. inductive only

D. inductive or resistive

108. A Transformer transforms____________?
comments icon0

A. current and voltage

B. power

C. voltage

D. current

109. A transformer can have regulation closer to zero___________?
comments icon0

A. on zero power factor

B. on overload

C. on full-load

D. on leading power factor
110. The secondary winding of which of the following transformers is always kept closed?
comments icon0

A. Potential transformer

B. Step-down transformer

C. Step-up transformer

D. Current transformer
111. Helical coils can be used on___________?
comments icon0
A. low voltage side of high kVA transformers

B. high voltage side of small capacity transformers

C. high frequency transformers

D. high voltage side of high kVA rating transformers

112. The efficiencies of transformers compared with that of electric motors of the same power are____________?
comments icon0
A. much higher

B. much smaller

C. about the same

D. somewhat smaller

E. none of the above

113. The thickness of laminations used in a transformer is usually____________?
comments icon0

A. 4 mm to 5 mm

B. 14 mm to 15 mm

C. 0.4 mm to 0.5 mm

D. 25 mm to 40 mm

114. The core used in high frequency transformer is usually___________?
comments icon0

A. copper core

B. cost iron core

C. air core

D. mild steel core

115. Noise level test in a transformer is a______________?
comments icon0

A. none of the above

B. type test

C. special test

D. routine test

116. Which of the following is not a part of transformer installation ?
comments icon0
A. Exciter

B. Conservator

C. Buchholz relay

D. Breather

117. Which of the following does not change in a transformer ?
comments icon0

A. Voltage

B. All of the above

C. Current

D. Frequency
118. The efficiency of a transformer will be maximum when_____________?
comments icon0

A. hysteresis losses = eddy current losses

B. copper losses = hysteresis losses

C. eddy current losses = copper losses

D. copper losses = iron losses
119. The hum in a transformer is mainly attributed to______________?
comments icon0

A. load changes

B. magnetostriction

C. oil in the transformer

D. mechanical vibrations

120. Power transformers are designed to have maximum efficiency at___________?
comments icon0

A. 50% full load

B. nearly full load

C. 70% full load

D. no load