21. To produce cathode spot in a mercury arc rectifier A. anode is heated B. tube is evacuated C. an auxiliary electrode is used D. low mercury vapour pressures are used Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option C No explanation is given for this question Let's Discuss on Board
22. A synchronous converter can be started A. by means of a small auxiliary motor B. from A.C. side as induction motor C. from D.C. side as D.C. motor D. any of the above methods Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option D No explanation is given for this question Let's Discuss on Board
23. In a single phase rotary converter the number of slip rings will be A. two B. three C. four D. six Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option A No explanation is given for this question Let's Discuss on Board
24. Which of the following rectifiers have been used extensively in supplying direct current for electroplating? A. Copper oxide rectifiers B. Selenium rectifiers C. Mercury arc rectifiers D. Mechanical rectifiers E. None of the above Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option B No explanation is given for this question Let's Discuss on Board
25. In a three-phase mercury arc rectifiers each anode conducts for A. One-third of a cycle B. One-fourth of a cycle C. One-half a cycle D. Two-third of a cycle Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option A No explanation is given for this question Let's Discuss on Board
26. Ageing of a selenium rectifier may change the output voltage by A. 5 to 10 per cent B. 15 to 20 per cent C. 25 to 30 per cent D. none of the above Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option A No explanation is given for this question Let's Discuss on Board
27. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be A. same B. less C. double D. three times Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option B No explanation is given for this question Let's Discuss on Board
28. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply? A. Mechanical rectifiers B. Copper oxide rectifiers C. Selenium rectifiers D. Electrolytic rectifiers Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option D No explanation is given for this question Let's Discuss on Board
29. The efficiency of the copper oxide rectifier seldom exceeds A. 90 to 95% B. 85 to 90% C. 80 to 85% D. 65 to 75% Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option D No explanation is given for this question Let's Discuss on Board
30. A rotary converter combines the function of A. An induction motor and a D.C. generator B. A synchronous motor and a D.C. generator C. A D.C. series motor and a D.C. generator D. None of the above Answer & Solution Discuss in Board Save for Later Answer & Solution Answer: Option B No explanation is given for this question Let's Discuss on Board
