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transformers MCQs

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

transformers Mcqs
1. A transformer core is laminated to__________?
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A. reduce copper losses

B. reduce hysteresis loss

C. reduce eddy current losses

D. reduce all above losses

2. The no load current in a transformer lags behind the applied voltage by an angle of about_____________?
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A. 90

B. 120?

C. 75

D. 180

3. Which type of winding is used in 3 phase shell-type transformer?
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A. Circular type

B. Sandwich type

C. Rectangular type

D. Cylindrical type

4. No-load current of a transformer has_____________?
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A. has small magnitude and low power factor

B. has small magnitude and high power factor

C. has high magnitude and high power factor

D. has high magnitude and low power factor

5. Spacers are provided between adjacent coils?
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A. to provide free passage to the cooling oil

B. to insulate the coils from each other

C. both A. and (b)

D. none of the above

6. A common method of cooling a power transformer is_______________?
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A. any of the above

B. natural air cooling

C. oil cooling

D. air blast cooling

7. The noise resulting from vibrations of laminations set by magnetic forces, is termed as_________________?
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A. zoom

B. magnetostrication

C. hum

D. boo

8. Delta/star transformer works satisfactorily when______________?
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A. on balanced as well as unbalanced loads

B. none of the above

C. load is balanced only

D. load is unbalanced only

9. The path of a magnetic flux in a transformer should have______________?
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A. high reluctance

B. low resistance

C. high resistance

D. low reluctance
10. The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be___________?
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A. 1600 W

B. 800 W

C. 6400 W

D. 400 W
11. Iron loss of a transformer can be measured by____________?
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A. any type of wattmeter

B. frequency meter

C. low power factor wattmeter

D. unity power factor wattmeter

12. Which winding of the transformer has less cross-sectional area?
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A. Low voltage winding

B. Primary winding

C. Secondary winding

D. High voltage winding
13. Which of the following property is not necessarily desirable in the material for transformer core ?
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A. Low hysteresis loss

B. Mechanical strength

C. High permeability

D. High thermal conductivity
14. The magnetising current of a transformer is usually small because it has___________?
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A. laminated silicon steel core

B. small air gap

C. large leakage flux

D. fewer rotating parts

15. In a transformer the resistance between its primary and secondary should be_____________?
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A. 1000 Q

B. infinity

C. zero

D. 10 Q

16. Harmonics in transformer result in___________?
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A. increased I2R losses

B. increased core losses

C. all of the above

D. magnetic interference with communication circuits

17. Which of the following parts of a transformer is visible from outside ?
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A. Primary winding

B. Bushings

C. Core

D. Secondary winding

18. In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of_________________?
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A. more than 15 A

B. none of the above

C. less than 15 A

D. 15 A

19. Losses which occur in rotating electric machines and do not occur in transformers are___________?
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A. hysteresis and eddy current losses

B. friction and windage losses

C. copper losses

D. magnetic losses

20. The power transformer is a constant______________?
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A. voltage device

B. power device

C. main flux device

D. current device