Rectifiers

41. The ionization potential of mercury is approximately

  1. 5.4 V
  2. 8.4 V
  3. 10.4 V
  4. 16.4 V

Correct answer: (C)
10.4 V

42. The metal rectifiers are preferred to valve rectifiers due to which of the following advantages?

  1. They are mechanically strong
  2. They do not require any voltage for filament heating
  3. Both (a) and (b)
  4. None of the above

Correct answer: (C)
Both (a) and (b)

43. The metal rectifiers, as compared to mercury arc rectifiers

  1. operate on low temperatures
  2. can operate on high voltages
  3. can operate on heavy loads
  4. give poor regulation

Correct answer: (A)
operate on low temperatures

44. The potential drop in the arc, in a mercury arc rectifier, varies

  1. 0.05 V to 0.2 V per cm length of the arc
  2. 0.5 V to 1.5 V per cm length of the arc
  3. 2 V to 3.5 V per cm length of the arc
  4. none of the above

Correct answer: (D)
none of the above

45. The voltage drop at anode, in a mercury arc rectifier is due to

  1. self restoring property of mercury
  2. high ionization potential
  3. energy spent in overcoming the electrostatic field
  4. high temperature inside the rectifier

Correct answer: (C)
energy spent in overcoming the electrostatic field

46. The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following

  1. anode drop and cathode drop
  2. anode drop and arc drop
  3. cathode drop and arc drop
  4. anode drop, cathode drop and arc drop

Correct answer: (D)
anode drop, cathode drop and arc drop

47. 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

Correct answer: (C)
an auxiliary electrode is used

48. When a rectifier is loaded which of the following voltage drops take place?

  1. Voltage drop in transformer reactance
  2. Voltage drop in resistance of transformer and smoothing chokes
  3. Arc voltage drop
  4. All of the above

Correct answer: (D)
All of the above

49. Which of the following AC. motors is usually used in large motor-generator sets?

  1. Synchronous motor
  2. Squirrel cage induction motor
  3. Slip ring induction motor
  4. Any of the above

Correct answer: (A)
Synchronous motor

50. Which of the following are the applications of D.C. system?

  1. Battery charging work
  2. Arc welding
  3. Electrolytic and electro-chemical processes
  4. Arc lamps for search lights
  5. All of the above

Correct answer: (E)
All of the above

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