Transformer Multiple Choice Questions Answers In English - 01

1. The purpose of providing an iron core in a transformer is to
(A) provide support to windings
(B) reduce hysteresis loss
(C) decrease the reluctance of the magnetic path
(D) reduce eddy current losses
Ans: C

2. Which of the following is not a part of transformer installation ?
(A) Conservator
(B) Breather
(C) Buchholz relay
(D) Exciter
Ans: D

3. In a transformer routine efficiency depends upon
(A) supply frequency
(B) load current
(C) power factor of load
(D) both (B) and (C)
Ans: D

4. In the transformer the function of a conservator is to
(A) provide fresh air for cooling the transformer
(B) supply cooling oil to transformer in time of need
(C) protect the transformer from damage when oil expends due to heating
(D) none of the above
Ans: C

5. Natural oil cooling is used for transformers up to a rating of
(A) 3000 kVA
(B) 1000 kVA
(C) 500 kVA
(D) 250 kVA
Ans: A

6. Power transformers are designed to have maximum efficiency at
(A) nearly full load
(B) 70% full load
(C) 50% full load
(D) no load
Ans: A

7. The maximum efficiency of a distribution transformer is
(A) at no load
(B) at 50% full load
(C) at 80% full load
(D) at full load
Ans: B

8. While conducting short-circuit test on a transformer the following side is short circuited
(A) High voltage side
(B) Low voltage side
(C) Primary side
(D) Secondary side
Ans: B

9. In the transformer following winding has got more cross-sectional area
(A) Low voltage winding
(B) High voltage winding
(C) Primary winding
(D) Secondary winding
Ans: A

10. A transformer transforms
(A) voltage
(B) current
(C) power
(D) frequency
Ans: C

11. A transformer cannot raise or lower the voltage of a D.C. supply because
(A) there is no need to change the D.C. voltage
(B) a D.C. circuit has more losses
(C) Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero
(D) none of the above
Ans: C

12. Greater the secondary leakage flux
(A) less will be the secondary induced e.m.f.
(B) less will be the primary induced e.m.f.
(C) less will be the primary terminal voltage
(D) none of the above
Ans: A

13. The purpose of providing iron core in a step-up transformer is
(A) to provide coupling between primary and secondary
(B) to increase the magnitude of mutual flux
(C) to decrease the magnitude of mag-netizing current
(D) to provide all above features
Ans: C

14. The power transformer is a constant
(A) voltage device
(B) current device
(C) power device
(D) main flux device
Ans: D

15. Two transformers operating in parallel will share the load depending upon their
(A) leakage reactance
(B) per unit impedance
(C) efficiencies
(D) ratings
Ans: B

16. Which of the following does not change in a transformer ?
(A) Current
(B) Voltage
(C) Frequency
(D) All of the above
Ans: C

17. In a transformer the energy is conveyed from primary to secondary
(A) through cooling coil
(B) through air
(C) by the flux
(D) none of the above
Ans: C

18. A transformer core is laminated to
(A) reduce hysteresis loss
(B) reduce eddy current losses
(C) reduce copper losses
(D) reduce all above losses
Ans: B

19. The degree of mechanical vibrations produced by the laminations of a transformer depends on
(A) tightness of clamping
(B) gauge of laminations
(C) size of laminations
(D) all of the above
Ans: D

20. The no-load current drawn by transformer is usually what per cent of the full-load current ?
(A) 0.2 to 0.5 per cent
(B) 2 to 5 per cent
(C) 12 to 15 per cent
(D) 20 to 30 per cent
Ans: B