In this article, we shared the rectifiers & converters multiple choice questions and answers.
Rectifiers & Converters MCQ
The below list provides all the multiple-choice questions related to the rectifiers & converters.
Answers are available at the bottom of the article.
1. In a mercury arc rectifier, the anode is usually made of
| A) | copper |
| B) | silver |
| C) | aluminium |
| D) | tungsten |
| E) | graphite |
2. In a grid control of mercury arc rectifiers when it is made positively relative to the cathode, then it____ the electrons on their may to the anode.
| A) | decelerates |
| B) | none of these answers |
| C) | accelerates |
| D) | any of these answers |
3. If cathode and anode connections in a mercury arc rectifier are interchanged
| A) | the rectifier will operate at reduced efficiency |
| B) | both ion and electron streams will move in the same direction |
| C) | internal losses will be reduced |
| D) | the rectifier will not operate |
4. Copper oxide rectifier is usually designed not to operate above
| A) | 10°C |
| B) | 30°C |
| C) | 20°C |
| D) | 45°C |
5. In which of the following equipment direct current is needed?
| A) | Time switches |
| B) | All of these answers |
| C) | Telephones |
| D) | Relays |
6. Which of the following is the loss within the mercury arc rectifier chamber?
| A) | All of these answers |
| B) | Voltage drop in the arc |
| C) | Voltage drop at the anode |
| D) | Voltage drop at the cathode |
7. The efficiency of the copper oxide rectifier seldom exceeds
| A) | 80 to 85% |
| B) | 65 to 75% |
| C) | 90 to 95% |
| D) | 85 to 90% |
8. A rotary converter is a single machine with
| A) | one armature and two fields |
| B) | one armature and one field |
| C) | two armatures and one field |
| D) | none of these answers |
9. A rotary converter combines the function of
| A) | a synchronous motor and a D.C. generator. |
| B) | an induction motor and a D.C. generator |
| C) | none of these answers |
| D) | a D.C. series motor and a D.C. generator |
10. To produce cathode spot in a mercury arc rectifier
| A) | low mercury vapour pressures are used |
| B) | tube is evacuated |
| C) | anode is heated |
| D) | an auxiliary electrode is used |
11. Which of the following metals is generally manufactured by the electrolysis process?
| A) | Aluminium |
| B) | Load |
| C) | None of these answers |
| D) | Zinc |
| E) | Copper |
12. In selenium rectifiers efficiencies ranging from ____ to ____ percent are attainable
| A) | 40, 50 |
| B) | 60, 70 |
| C) | 25, 35 |
| D) | 75, 85 |
13. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
| A) | same |
| B) | double |
| C) | less |
| D) | three times |
14. The voltage drop at the anode, in a mercury arc rectifier, is due to
| A) | high ionization potential |
| B) | energy spent in overcoming the electrostatic field |
| C) | self restoring property of mercury |
| D) | high temperature inside the rectifier |
15. In a mercury arc rectifier ____ flow from anode to cathode
| A) | electrons |
| B) | ions |
| C) | any of these answers |
| D) | ions and electrons |
16. A rotary converter operates at a
| A) | high power factor |
| B) | zero power factor |
| C) | none of these answers |
| D) | low power factor |
17. Which of the following rectifiers have been used extensively in supplying direct current for electroplating?
| A) | Copper oxide rectifiers |
| B) | Mechanical rectifiers |
| C) | Mercury arc rectifiers |
| D) | None of these answers |
| E) | Selenium rectifiers |
18. A commutating rectifier consists of a commutator driven by
| A) | an induction motor |
| B) | a D.C. series motor |
| C) | a synchronous motor |
| D) | a D.C. shunt motor |
19. The metal rectifiers, as compared to mercury arc rectifiers
| A) | can operate on heavy loads |
| B) | none of these answers |
| C) | can operate on high voltages |
| D) | give poor regulation |
| E) | operate on low temperatures |
20. In a three-phase mercury arc rectifiers each anode conducts for
| A) | one-half a cycle |
| B) | one-third of a cycle |
| C) | one-fourth of a cycle |
| D) | two-third of a cycle |
21. Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of
| A) | 200 A at 200 V |
| B) | 100 A at 100 V |
| C) | 300 A at 300 V |
| D) | 400 A at 400 V |
| E) | 500 A at 500 V |
22. In a rotary converter armature currents are
| A) | partly a.c. and partly d.c. |
| B) | a.c. only |
| C) | d.c. only |
| D) | none of these answers |
23. A rotary converter in general construction and design, is more or less like
| A) | any D.C. machine |
| B) | an alternator |
| C) | a transformer |
| D) | an induction motor |
24. A mercury arc rectifier possesses____ regulation characteristics
| A) | none of these answers |
| B) | straight line |
| C) | curved line |
| D) | exponential |
25. The applications of selenium rectifiers are usually limited to the potential of
| A) | 60 V |
| B) | 10 V |
| C) | 30 V |
| D) | 100 V |
| E) | 200 V |
26. On which of the following factors does the number of phases for which a rectifier should be designed depend?
| A) | The power factor of the system should be high |
| B) | The voltage regulation of the rectifier should be low |
| C) | all of these answers |
| D) | The rectifier supply transformer should be utilized to the best advantage |
| E) | In the output circuit there should be no harmonics |
27. It is the____ of the transformer on which the magnitude of the angle of overlap depends.
| A) | capacitance |
| B) | any of these answers |
| C) | leakage reactance |
| D) | resistance |
28. In mercury arc rectifiers having a grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as____
| A) | none of these answers |
| B) | critical grid voltage |
| C) | any of these answers |
| D) | maximum grid voltage |
29. Which of the following A.C. motors is usually used in large motor-generator sets?
| A) | Slip ring induction motor |
| B) | Synchronous motor |
| C) | Squirrel cage induction motor |
| D) | Slip ring induction motor |
30. Which of the following statement is incorrect?
| A) | Copper oxide rectifier is not a perfect rectifier |
| B) | Copper oxide rectifier is a linear device |
| C) | Copper oxide rectifier is not stable during early life |
| D) | Copper oxide rectifier finds use in control circuits |
| E) | Copper oxide rectifier has a low efficiency |
31. In a phase-shift control method, the phase shift, between anode and grid voltages can be achieved by means of
| A) | synchronous generator |
| B) | induction regulator |
| C) | shunt motor |
| D) | synchronous motor |
32. 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 these answers |
| E) | none of these answers |
33. Normally, which of the following is used, when a large-scale conversion. from A.C. to D.C. power is required?
| A) | Mercury arc rectifier |
| B) | Motor-generator set |
| C) | Motor converter |
| D) | Rotary converter |
34. The efficiency of an electrolytic rectifier is nearly
| A) | 0.6 |
| B) | 0.8 |
| C) | 0.7 |
| D) | 0.4 |
35. Which of the following mercury arc rectifier will deliver the least undulating current?
| A) | Single-phase |
| B) | Two-phase |
| C) | Six-phase |
| D) | Three-phase |
36. In a single phase rotary converter the number of slip rings will be
| A) | six |
| B) | four |
| C) | two |
| D) | three |
| E) | none of these answers |
37. The voltage drop between the anode and cathode, of a mercury arc rectifier comprises the following
| A) | cathode drop and arc drop |
| B) | anode drop and cathode drop |
| C) | anode drop and arc drop |
| D) | anode drop, cathode drop and arc drop |
38. Which of the following is reversible in action?
| A) | Motor converter |
| B) | Rotary converter |
| C) | Any of these answers |
| D) | Motor generator set |
| E) | None of these answers |
39. In a mercury pool rectifier, the voltage drop across its electrodes
| A) | is inversely proportional to load |
| B) | varies exponentially with the load current |
| C) | is directly proportional to load |
| D) | is almost independent of load current |
40. In the phase-shift control method the control is carried out by varying the of grid voltage.
| A) | none of these answers |
| B) | polarity |
| C) | any of these answers |
| D) | phase |
| E) | magnitude |
41. In a mercury arc rectifier characteristic blue luminosity is due to
| A) | ionization |
| B) | high temperature |
| C) | colour of mercury |
| D) | electron streams |
42. Which of the following are the applications of D.C. system?
| A) | Electrolytic and electro-chemical processes |
| B) | Battery charging work |
| C) | Arc lamps for search lights |
| D) | All of these answers |
| E) | Arc welding |
43. The ignited or auxiliary anode in mercury arc rectifier is made of
| A) | aluminium |
| B) | boron carbide |
| C) | graphite |
| D) | copper |
44. Selenium rectifier can be operated at temperatures as high as
| A) | 40°C |
| B) | 25°C |
| C) | 75°C |
| D) | 60°C |
45. In which of the following applications, direct current is absolutely essential?
| A) | Illumination. |
| B) | Electrolysis |
| C) | Variable speed operation |
| D) | Traction |
46. The potential drop in the arc, in a mercury arc rectifier, varies
| A) | 0.5 V to 1.5 V per cm length of the arc |
| B) | 0.05 V to 0.2 V per cm length of the arc |
| C) | 2V to 3.5V per cm length of the arc |
| D) | none of these answers |
47. The metal rectifiers are preferred to valve rectifiers due to which of the following advantages?
| A) | None of these answers |
| B) | They do not require any voltage for filament heating |
| C) | They are mechanically strong |
| D) | They are mechanically strong and do not require any voltage for filament heating |
48. Mercury, in arc rectifiers, is chosen for cathode because
| A) | its ionization potential is relatively low |
| B) | all of these answers |
| C) | its atomic weight is quite high |
| D) | its boiling point and specific heat are low |
| E) | it remains in a liquid state at ordinary temperature |
49. In a glass bulb mercury arc rectifier the maximum current rating is restricted to
| A) | 1500 A |
| B) | 2000 A |
| C) | 500 A |
| D) | 1000 A |
50. Ageing of a selenium rectifier may change the output voltage by
| A) | 25 to 30 per cent |
| B) | 5 to 10 per cent |
| C) | 15 to 20 per cent |
| D) | none of these answers |
51. Which of the following rectifiers are primarily used for charging of low voltage batteries from A.C. supply?
| A) | Copper oxide rectifiers |
| B) | Mercury arc rectifiers |
| C) | Mechanical rectifiers |
| D) | Selenium rectifiers |
| E) | Electrolytic rectifiers |
52. The internal efficiency of a mercury arc rectifier depends on
| A) | r.m.s. value of current |
| B) | voltage only |
| C) | none of these answers |
| D) | voltage and current |
| E) | current only |
53. The ionization potential of mercury is approximately
| A) | 16.4 V |
| B) | 8.4 V |
| C) | 5.4 V |
| D) | 10.4 V |
54. The advantage of mercury arc rectifier is that
| A) | all of these answers |
| B) | it has high efficiency |
| C) | it is light in weight and occupies small floor space |
| D) | it is comparatively noiseless |
| E) | It has a high overload capacity |
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