Most Important Transformer 50 MCQ

Most Important Transformer MCQ (50 MCQ)
Answer লেখা ইমেজে ক্লিক করলে সঠিক উত্তরটি দেখাবে।

1. Oil is provided in an oil filled transformer for
A. Insulation
B. cooling
C. both cooling and insulation.
D. Lubrication

2. The basic function of transformer is to change?
A. the level voltage
B. the level frequency
C. power factor level
D. power level

3. Transformer is used for—
A. to step down voltage
B. to step up and step down primary voltage
C. to step up voltage
D. None of above

4.Breather is provided in a transformer to
A. Absorb moisture of air during breathing.
B. filter of transformer oil
C. provide cold air in transformer
D. None of above

5. The leakage flux in a transformer depends upon
A. the load current.
B. the frequency.
C. the mutual flux.
D. the applied voltage.

6. What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?
A. 32kv
B. 16kv
C. 4kv
D. 8kV

7. The copper loss of a transformer at full load is 40W. What would be at half load-
A. 20W
B. 80W
C. 40W
D. 10W

8.When a 6 V battery is connected across the primary of a transformer with a turns ratio of 8, the secondary voltage is
A. 48v
B. 6v
C. 8v
D. 0v

9. The main purpose of performing open circuit test in a transformer is to measure its–
A. core loss
B. copper loss
C. insulation resistance
D. total loss

10. When a 400Hz transformer is operated at 50 Hz, its KVA ratings is–
A. unaffected
B. reduced to 1/8
C. Increased by 8 times
D. None of above.

11. What is the condition for maximum efficiency of a transformer?
A. when copper loss = core loss
B. when transformer run by unity power factor
C. when copper loss = eddy current loss
D.when copper loss = hysteresis loss

12. Lamination of transformer core is made of
A. cast iron
B. silicon steel.
C. cast steel
D. aluminium

13. Which of the following is minimized by laminating the core of a transformer?
A. Eddy current loss.
B. Hysteresis loss.
C. Copper loss
D. Stray loss

14. Does the transformer draw any current when secondary is open?
A. Yes
B. No

15. When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is-
A. 24v
B. 120v
C. 240v
D. 440v

16. The input power under no load condition of transformer consists of
A. core losses and very small amount of copper loss in primary.
B. copper loss in transformers.
C. core loss in transformers.
D. None of above.

17. Transformers operating in parallel will share the load depending upon their-
A. Rating
B. Percentage impedance.
C. Leakage reactance.
D. None of above

18. Which of the following is not a basic element of a transformer?
A. primary winding
B. secondary winding
C. mutual flux
D. core

19. At relatively light load, transformer efficiency is low because-.
A. transformer losses are high
B. secondary output is low
C. fixed loss is high in proportion to the output
D. Cu loss is small

20. A transformer transform-
A. voltage and currrent
B. voltage
C. current
D. frequency

21. When AC supply is given to the transformer, the flux will depend on…….
A. Current
B. Voltage
C. Frequency
D. Voltage and Frequency

22.No-load test on a transformer is carried out to determine-
A. copper loss
B. magnetising current and no-load current
C. magnetising current
D. all of above.

23. Which of the following losses varies with load in transformer?
A. Copper loss.
B. Core loss
C. Transfomer all losses
D. None of above

24. A transfomer has negative voltage regulation when its load power factor is–
A. lagging
B. leading
C. unity
D. None of above

25. The essential condition for parallel operation of two single-phase transformer is that they should have the same–
A. polarity
B. KVA ratings
C. voltage ratio

26. Which one is used for constant street light load?
A. current transformer
B. Constant current transformer
C. power transformer
D. potential transformer

27. Which of the following losses remain constant during normal operation of transformer?
A. Copper loss
B. Transformer all losses
C. Core loss
D. None of above

28. Iron loss in transformer can be determined by-
A. open circuit test.
B. short circuit test.

29. Transformer core are laminated in order to-
A. simplify it’s construction
B. minimize eddy current loss
C. reduce cost
D. reduce hysteresis loss

30. The main purpose of performing short circuit test in a transformer is to measure its–
A. Copper Loss
B. Core Loss
C. Total Loss
D. Insulation resistance

31. The path of a magnetic flux in a transformer should have
A. low resistance
B. low reluctance
C. high resistance
D. high reluctance

32. No-load current in a transformer
A. lags behind the voltage by about 75°
B. leads the voltage by about 75°
C. lags behind the voltage by about 15°
D. leads behind the voltage by about 25°

33. Which of the following is not a part of transformer ?
A. Breather
B. Conservator
C. Exciter
D. Buchholz relay

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

35. Which winding in a transformer has more number of turns ?
A. Primary winding
B. Secondary winding
C. High voltage winding
D. Low voltage winding

36. In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are
A. core losses
B. copper losses
C. both A and B
D. none of the above

37. Power transformers are designed to have maximum efficiency at
A. 80% full load
B. 50% full load
C. nearly full load
D. no load

38. The maximum efficiency of a distribution transformer is
A. at full load
B. at 70% full load
C. at 50% full load
D. at no load

39. Flash point of transformer insulating oil should be more than
A. 100°C.
B. 140°C.
C. 45°C.
D. 35°C.

40. Noise of transformer mainly due to
A. noise generated by cooling fans.
B. magnetostriction in iron core.
C. mechanical vibration.
D. all of above

41. The tap changer in an electrical power transformer is provided on
A. LV winding.
B. HV winding.
C. either LV or HV winding.
D. both LV and HV winding.

42. The transformer ratings are usually expressed in terms of
A. KVA
B. KW
C. KVAR
D. Volts

43. A Buchholz relay can be installed on-
A. welding transformers
B. air cooled transformers
C. oil cooled transformers
D. all of above

44. In a transformer the resistance between its primary and secondary is
A. zero
B. infinite
C. 1 ohm
D. 10000 ohm

45. If the supply frequency to the transformer is increased, the iron loss will
A. remain same
B. decrease
C. increase
D. any of the above

46. Which type of winding is used in 3phase shell-type transformer ?
A. Cylindrical type
B. Circular type
C. Rectangular type
D. Sandwich type

47. The secondary winding of which of the following transformers is always kept closed ?
A. CT
B. PT
C. Step-up transformer
D. Step-down transformer

48. The efficiency of two identical transformers under load conditions can be determined by
A. back-to-back test
B. short circuit test
C. open circuit test
D. none of above

49. Which of the following loss in a transformer is zero even at full load ?
A. Hysteresis loss
B. Eddy current loss
C. Core loss
D. Friction loss

50. If supply frequency of a transformer increases, the secondary output voltage of the transformer –
A. remains same.
B. increases.
C. decreases.
D. any of the above

Ans Sheet:
1C – 2A – 3B – 4A – 5A – 6B – 7D – 8D – 9A – 10B – 11A – 12B – 13A – 14A – 15C- 16A – 17A – 18C – 19C – 20A – 21D -22B – 23A – 24B – 25A – 26B – 27C – 28A – 29B – 30A – 31B – 32A – 33C – 34A – 35C – 36A – 37C – 38C – 39B – 40B – 41B – 42A – 43C – 44B – 45C – 46D – 47A – 48A – 49D – 50A

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