rectifiers and converters MCQs – Page 2

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

rectifiers and converters Mcqs
21. In a mercury pool rectifier, the voltage drop across its electrodes___________?
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A. is almost independent of load current

B. varies exponentially with the load current

C. is directly proportional to load

D. is inversely proportional to load

22. In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.
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A. decelerates

B. any of the above

C. none of the above

D. accelerates
23. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC supply ?
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A. Selenium rectifiers

B. Copper oxide rectifiers

C. Electrolytic rectifiers

D. Mercury arc rectifiers

E. Mechanical rectifiers

24. It is the_________of the transformer on which the magnitude of angle of overlap depends?
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A. leakage reactance

B. resistance

C. capacitance

D. any of the above

25. Ageing of a selenium rectifier may change the output voltage by__________?
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A. 5 to 10 per cent

B. none of the above

C. 15 to 20 per cent

D. 25 to 30 per cent

26. The internal efficiency of a mercury arc rectifier depends on___________?
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A. voltage only

B. current only

C. none of the above

D. voltage and current

E. r.m.s. value of current

27. Which of the following is the loss within the mercury arc rectifier chamber ?
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A. Voltage drop at the cathode

B. Voltage drop at the anode

C. Voltage drop in arc

D. All of the above
28. If cathode and anode connections in a mercury arc rectifier are inter changed_____________?
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A. the rectifier will not operate

B. internal losses will be reduced

C. both ion and electron streams will move in the same direction

D. the rectifier will operate at reduced efficiency

29. In a single phase rotary converter the number of slip rings will be_____________?
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A. three

B. none

C. two

D. four

E. six

30. A rotary converter combines the function of____________?
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A. none of the above

B. a D.C. series motor and a D.C. generator

C. an induction motor and a D.C. generator

D. a synchronous motor and a D.C. generator
31. Which of the following rectifiers have been used extensively in supplying direct current for electroplating ?
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A. Copper oxide rectifiers

B. None of the above

C. Mercury arc rectifiers

D. Mechanical rectifiers

E. Selenium rectifiers
32. Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of _____________?
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A. 400 A at 400 V

B. 500 A at 500 V

C. 200 A at 200 V

D. 100 A at 100 V

E. 300 A at 300 V

33. In a three-phase mercury arc rectifiers each anode conducts for____________?
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A. one-half a cycle

B. one-fourth of a cycle

C. one-third of a cycle

D. two-third of a cycle

34. Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required ?
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A. Mercury arc rectifier

B. Motor converter

C. Rotary converter

D. Motor-generator set

35. The cathdde voltage drop, in a mercury arc rectifier, is due to_____________?
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A. expenditure of energy in ionization

B. expenditure of energy in overcoming the electrostatic field

C. surface resistance

D. expenditure of energy in liberating electrons from the mercury
36. Which of the following are the applications of D.C. system ?
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A. Arc lamps for search lights

B. Arc welding

C. Electrolytic and electro-chemical processes

D. All of the above

E. Battery charging work

37. The advantage of mercury arc rectifier is that________________?
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A. it is comparatively noiseless

B. it is light in weight and occupies small floor space

C. it has high efficiency

D. it has high overload capacity

E. all of the above
38. In which of the following equipment direct current is needed ?
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A. Relays

B. All of the above

C. Telephones

D. Time switches

39. On which of the following factors the number of phases for which a rectifier should be designed depend ?
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A. In the output circuit there should be no harmonics

B. all of the above

C. The voltage regulation of the rectifier should be low

D. The power factor of the system should be high

E. The rectifier supply transformer should be utilized to the best ad-vantage

40. Which of the following statement is incorrect ?
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A. Copper oxide rectifier is not stable during early life

B. Copper oxide rectifier is not a perfect rectifier

C. Copper oxide rectifier finds use in control circuits

D. Copper oxide rectifier has a low efficiency

E. Copper oxide rectifier is a linear device