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MCQs

Total Questions : 130 | Page 3 of 13 pages
Question 21. To produce cathode spot in a mercury arc rectifier
  1.    anode is heated
  2.    tube is evacuated
  3.    an auxiliary electrode is used
  4.    low mercury vapour pressures are used
 Discuss Question
Answer: Option C. -> an auxiliary electrode is used
Question 22. A synchronous converter can be started
  1.    by means of a small auxiliary motor
  2.    from A.C. side as induction motor
  3.    from D.C. side as D.C. motor
  4.    any of the above methods
 Discuss Question
Answer: Option D. -> any of the above methods
Question 23. In a single phase rotary converter the number of slip rings will be
  1.    two
  2.    three
  3.    four
  4.    six
 Discuss Question
Answer: Option A. -> two
Question 24. Which of the following rectifiers have been used extensively in supplying direct current for electroplating?
  1.    Copper oxide rectifiers
  2.    Selenium rectifiers
  3.    Mercury arc rectifiers
  4.    Mechanical rectifiers
  5.    None of the above
 Discuss Question
Answer: Option B. -> Selenium rectifiers
Question 25. In a three-phase mercury arc rectifiers each anode conducts for
  1.    One-third of a cycle
  2.    One-fourth of a cycle
  3.    One-half a cycle
  4.    Two-third of a cycle
 Discuss Question
Answer: Option A. -> One-third of a cycle
Question 26. Ageing of a selenium rectifier may change the output voltage by
  1.    5 to 10 per cent
  2.    15 to 20 per cent
  3.    25 to 30 per cent
  4.    none of the above
 Discuss Question
Answer: Option A. -> 5 to 10 per cent
Question 27. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply?
  1.    Mechanical rectifiers
  2.    Copper oxide rectifiers
  3.    Selenium rectifiers
  4.    Electrolytic rectifiers
 Discuss Question
Answer: Option D. -> Electrolytic rectifiers
Question 28. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
  1.    same
  2.    less
  3.    double
  4.    three times
 Discuss Question
Answer: Option B. -> less
Question 29. The efficiency of the copper oxide rectifier seldom exceeds
  1.    90 to 95%
  2.    85 to 90%
  3.    80 to 85%
  4.    65 to 75%
 Discuss Question
Answer: Option D. -> 65 to 75%
Question 30. A rotary converter combines the function of
  1.    an induction motor and a D.C. generator
  2.    a synchronous motor and a D.C. generator
  3.    a D.
  4.    none of the above
 Discuss Question
Answer: Option B. -> a synchronous motor and a D.C. generator

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