multiple choice questions on transformer # 7

 
                             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) The transformer efficiency at relatively light loads is quite low. This is due to
A) small copper losses
B) small secondary output
C) high fixed loss in comparison to the output
D) poor power factor

Ans:C

2) For a transformer to be tested at full load conditions but consuming only losses from the mains, we do
A) load test
B) open circuit and short circuit tests
C) back to back test
D) none of the above

Ans:C

3) A 10 KVA, 400 V/200 V single phase transformer with 10% impedance draws a steady short circuit line current of
A) 50 A
B) 150 A
C) 250 A
D) 350 A

Ans:C

4) A single phase transformer has a maximum efficiency of 90% at full load and unity power factor. Efficiency at half load at the same power factor is
A) 86.7%
B) 88.26%
C) 88.9%
D) 87.8%

Ans:D

5) When a no load test is carried out on hv side of 1000/100 V single phase transformer with 100 V winding open, the watt meter reads 110 watts. If the test is repeated on lv side with 1000 V winding open. The wattmeter will read
A) 11 W
B) 110 W
C) 1.1 W
D) 1100 W

Ans:B

6) The efficiency of a 100 KVA transformer is 0.98 at full as well as half load. For this transformer at full load the copper loss
A) is less than core loss
B) is equal to core loss
C) is more than core loss
D) none of the above

Ans:C

7) what is load at which maximum efficiency occurs in case of a 100 KVA transformer with iron losses of 1KW and full load copper loss of 2 KW
A) 100 KVA
B) 70.7 KVA
C) 50.5 KVA
D) 25.2 KVA

Ans:B

8) The transformer efficiency , under heavy loads is comparatively low due to
A) large increase in copper losses in comparison to the output
B) large increase in iron losses
C) drop in power factor
D) none of the above

Ans:A

9) If P1 and P2 be the iron and copper losses of a transformer at full load and the maximum efficiency is at 75% of the full load, then what is the ratio of P1 and P2?
A) 9/16
B) 10/16
C) 3/4
D) 3/16

Ans:A

10) Power transformers are designed to have maximum efficiency around........... full load
A) nearly
B) 70% of
C) 50% of
D) 25% of

Ans:A

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