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rectifiers and converters MCQs

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

rectifiers and converters Mcqs

1. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be___________?
0

A. three times

B. less

C. double

D. same

2. In a mercury arc rectifier characteristic blue luminosity is due to_____________?
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A. electron streams

B. high temperature

C. colour of mercury

D. ionization

3. Selenium rectifier can be operated at temperatures as high as____________?
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A. 25C

B. 60C

C. 75C

D. 40C

4. In a mercury arc rectifier, the anode is usually made of_____________?
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A. copper

B. tungsten

C. aluminium

D. graphite

E. silver

5. A commutating rectifier consists of commutator driven by___________?
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A. a D.C. series motor

B. a synchronous motor

C. an induction motor

D. a D.C. shunt motor

6. A rotary converter in general construction and design, is more or less like___________?
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A. an alternator

B. any D.C. machine

C. a transformer

D. an induction motor

7. In which of the following appUcations, direct current is absolutely essential ?
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A. Variable speed operation

B. Electrolysis

C. Illumination

D. Traction

8. In a mercury arc rectifier________ flow from anode to cathode
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A. ions

B. any of the above

C. ions and electrons

D. electrons

9. The ionization potential of mercury is approximately_____________?
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A. 5.4 V

B. 10.4 V

C. 16.4 V

D. 8.4 V

10. In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as______________?
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A. maximum grid voltage

B. critical grid voltage

C. none of the above

D. any of the above

11. The efficiency of the copper oxide rectifier seldom exceeds____________?
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A. 80 to 85%

B. 90 to 95%

C. 85 to 90%

D. 65 to 75%

12. To produce cathode spot in a mercury arc rectifier______________?
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A. low mercury vapour pressures are used

B. anode is heated

C. an auxiliary electrode is used

D. tube is evacuated

13. In a glass bulb mercury arc rectifier the maximum current rating is restricted to___________?
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A. 1500 A

B. 500 A

C. 2000 A

D. 1000 A

14. The applications of selenium rectifiers are usually limited to potential of_____________?
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A. 200 V

B. 10 V

C. 30 V

D. 100 V

E. 60 V

15. With a motor converter it is possible to obtain D.C. voltage only upto__________?
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A. 200-100 V

B. 10001200 V

C. 17002000 V

D. 600800 V

16. A rotary converter operates at a______________?
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A. high power factor

B. low power factor

C. none of the above

D. zero power factor

17. Which of the following AC. motors is usually used in large motor-generator sets?
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A. Squirrel cage induction motor

B. Any of the above

C. Slip ring induction motor

D. Synchronous motor

18. The efficiency of an electrolytic rectifier is nearly____________?
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A. 70%

B. 80%

C. 40%

D. 60%

19. Mercury, in arc rectifiers, is chosen for cathode because________________?
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A. all of the above

B. its ionization potential is relatively low

C. it remains in liquid state at ordinary temperature

D. its atomic weight is quite high

E. its boiling point and specific heat are low

20. A mercury arc rectifier possesses __________ regulation characteristics
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A. curved line

B. exponential

C. none of the above

D. straight line

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