multiple choice questions on transformer # 5

                       Hi friends, this post is about transformer objectives. These are some of the questions asked in previous question papers of Gate, IES and other competitive exams. check out and comment if you have any doubts.....

1) In a transformer ................ decrease with the increase in leakage flux
A) primary induced emf
B) secondary induced emf
C) secondary terminal voltage
D) none of the above

Ans:C

2) A transformer is supplying pure resistive (unity pf) load. The power factor on primary side will be
A) about 0.95 (lead)
B) about 0.95 (lag)
C) zero
D) unity

Ans:B

3) In a power transformer, if in place of sinusoidal wave, a peaked wave voltage is fed to the primary
A) copper losses will be less
B) noise level will be reduced
C) iron losses will be more
D) iron losses will be less

Ans:D

4) Positive voltage regulation is an indication of ...............load
A) inductive
B) capacitive
C) either inductive or capacitive
D) pure resistive

Ans:C

5) In a transformer supplying inductive load
A) the secondary current results in equivalent primary current in phase opposition
B) the secondary terminal voltage is less than the secondary induced emf
C) the power factor on primary side will be lower than that of load
D) all of the above

Ans:D

6) In a power transformer iron losses remain practically constant from no-load to full load. This is because
A) core flux remains constant
B) leakage flux remains constant
C) both (A) and (B)
D) neither (A) nor (B)

Ans:A

7) If the percentage resistance of a power transformer for secondary side is 2.5 percent and turn ratio is 1:10, the percentage secondary resistance referred to primary will be
A) 25
B) 2.5
C) 0.25
D) 0.025

Ans:B

8) The total iron loss in a transformer core at normal flux density was measured at 25 Hz and at 50 Hz and was found to be 250W and 800 W respectively. The hysteresis loss at 50 Hz would be
A) 100 W
B) 150 W
C) 200 W
D) 600 W

Ans:C

9) 10 KVA, 400 V/200 V single phase transformer with a resistance of 3% and reactance of 6% is supplying a current of 50 A to a resistive load. The voltage across the load is
A) 194 V
B) 196 V
C) 198 V
D) 390 V

Ans:A

10) The full-load copper loss and iron loss of a transformer are 6400 W and 5000 W respectively. The copper loss and iron loss at half load will be, respectively
A) 3200 W and 2500 W
B) 3200 W and 5200 W
C) 1600 W and 1250 W
D) 1600 W and 5000 W

Ans:D

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