MCQOPTIONS
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MCQOPTIONS
This section includes 50 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
With a motor converter it is possible to obtain D.C. voltage only upto__________? |
| A. | 200-100 V |
| B. | 600—800 V |
| C. | 1000—1200 V |
| D. | 1700—2000 V |
| Answer» E. | |
| 2. |
Which of the following statement is incorrect ? |
| A. | Copper oxide rectifier is a linear device |
| B. | Copper oxide rectifier is not a perfect rectifier |
| C. | Copper oxide rectifier has a low efficiency |
| D. | Copper oxide rectifier finds use in control circuits |
| E. | Copper oxide rectifier is not stable during early life |
| Answer» B. Copper oxide rectifier is not a perfect rectifier | |
| 3. |
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» C. Mercury arc rectifiers | |
| 4. |
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 |
| E. | Mercury arc rectifiers |
| Answer» E. Mercury arc rectifiers | |
| 5. |
Which of the following methods may be used to convert A.C. system to D.C ? |
| A. | Rectifiers |
| B. | Motor converters |
| C. | Motor-generator sets |
| D. | Rotary converters |
| E. | All of the above |
| Answer» F. | |
| 6. |
Which of the following metals is generally manufactured by electrolysis process ? |
| A. | Load |
| B. | Aluminium |
| C. | Copper |
| D. | Zinc |
| E. | None of the above |
| Answer» C. Copper | |
| 7. |
Which of the following is the loss within the mercury arc rectifier chamber ? |
| A. | Voltage drop in arc |
| B. | Voltage drop at the anode |
| C. | Voltage drop at the cathode |
| D. | All of the above |
| Answer» E. | |
| 8. |
Which of the following is reversible in action ? |
| A. | Motor generator set |
| B. | Motor converter |
| C. | Rotary converter |
| D. | Any of the above |
| E. | None of the above |
| Answer» D. Any of the above | |
| 9. |
Which of the following are the applications of D.C. system ? |
| A. | Battery charging work |
| B. | Arc welding |
| C. | Electrolytic and electro-chemical processes |
| D. | Arc lamps for search lights |
| E. | All of the above |
| Answer» F. | |
| 10. |
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» D. low mercury vapour pressures are used | |
| 11. |
The voltage drop at anode, in a mercury arc rectifier is due to_____________? |
| A. | self restoring property of mercury |
| B. | high ionization potential |
| C. | energy spent in overcoming the electrostatic field |
| D. | high temperature inside the rectifier |
| Answer» D. high temperature inside the rectifier | |
| 12. |
The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following_____________? |
| A. | anode drop and cathode drop |
| B. | anode drop and arc drop |
| C. | cathode drop and arc drop |
| D. | anode drop, cathode drop and arc drop |
| Answer» E. | |
| 13. |
The potential drop in the arc, in a mercury arc rectifier, varies_____________? |
| A. | 0.05 V to 0.2 V per cm length of the arc |
| B. | 0.5 V to 1.5 V per cm length of the arc |
| C. | 2 V to 3.5 V per cm length of the arc |
| D. | none of the above |
| Answer» D. none of the above | |
| 14. |
The ionization potential of mercury is approximately_____________? |
| A. | 5.4 V |
| B. | 8.4 V |
| C. | 10.4 V |
| D. | 16.4 V |
| Answer» D. 16.4 V | |
| 15. |
The internal efficiency of a mercury arc rectifier depends on___________? |
| A. | voltage only |
| B. | current only |
| C. | voltage and current |
| D. | r.m.s. value of current |
| E. | none of the above |
| Answer» B. current only | |
| 16. |
The ignited or auxiliary anode in mercury arc rectifier is made of____________? |
| A. | graphite |
| B. | boron carbide |
| C. | aluminium |
| D. | copper |
| Answer» C. aluminium | |
| 17. |
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» E. | |
| 18. |
The efficiency of an electrolytic rectifier is nearly____________? |
| A. | 80% |
| B. | 70% |
| C. | 60% |
| D. | 40% |
| Answer» D. 40% | |
| 19. |
The cathdde voltage drop, in a mercury arc rectifier, is due to_____________? |
| A. | expenditure of energy in ionization |
| B. | surface resistance |
| C. | expenditure of energy in overcoming the electrostatic field |
| D. | expenditure of energy in liberating electrons from the mercury |
| Answer» E. | |
| 20. |
The applications of selenium rectifiers are usually limited to potential of_____________? |
| A. | 10 V |
| B. | 30 V |
| C. | 60 V |
| D. | 100 V |
| E. | 200 V |
| Answer» E. 200 V | |
| 21. |
The advantage of mercury arc rectifier is that________________? |
| A. | it is light in weight and occupies small floor space |
| B. | it has high efficiency |
| C. | it has high overload capacity |
| D. | it is comparatively noiseless |
| E. | all of the above |
| Answer» F. | |
| 22. |
On which of the following factors the number of phases for which a rectifier should be designed depend ? |
| A. | The voltage regulation of the rec¬tifier should be low |
| B. | In the output circuit there should be no harmonics |
| C. | The power factor of the system should be high |
| D. | The rectifier supply transformer should be utilized to the best ad-vantage |
| E. | all of the above |
| Answer» F. | |
| 23. |
Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required ? |
| A. | Motor-generator set |
| B. | Motor converter |
| C. | Rotary converter |
| D. | Mercury arc rectifier |
| Answer» E. | |
| 24. |
Mercury, in arc rectifiers, is chosen for cathode because________________? |
| A. | its ionization potential is relatively low |
| B. | its atomic weight is quite high |
| C. | its boiling point and specific heat are low |
| D. | it remains in liquid state at ordi¬nary temperature |
| E. | all of the above |
| Answer» F. | |
| 25. |
It is the_________of the transformer on which the magnitude of angle of overlap depends? |
| A. | resistance |
| B. | capacitance |
| C. | leakage reactance |
| D. | any of the above |
| Answer» D. any of the above | |
| 26. |
In which of the following equipment direct current is needed ? |
| A. | Telephones |
| B. | Relays |
| C. | Time switches |
| D. | All of the above |
| Answer» E. | |
| 27. |
In selenium rectifiers efficiencies ranging from _______ to _______ percent are attainable? |
| A. | 25, 35 |
| B. | 40, 50 |
| C. | 60, 70 |
| D. | 75, 85 |
| Answer» E. | |
| 28. |
In phase-shift control method the control is carried out by varying the of grid voltage |
| A. | magnitude |
| B. | polarity |
| C. | phase |
| D. | any of the above |
| E. | none of the above |
| Answer» D. any of the above | |
| 29. |
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______________? |
| A. | maximum grid voltage |
| B. | critical grid voltage |
| C. | any of the above |
| D. | none of the above |
| Answer» C. any of the above | |
| 30. |
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» B. one-fourth of a cycle | |
| 31. |
In a single phase rotary converter the number of slip rings will be_____________? |
| A. | two |
| B. | three |
| C. | four |
| D. | six |
| E. | none |
| Answer» B. three | |
| 32. |
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» C. double | |
| 33. |
In a rotary converter armature currents are______________? |
| A. | d.c. only |
| B. | a.c. only |
| C. | partly a.c. and partly d.c. |
| Answer» D. | |
| 34. |
In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of______________? |
| A. | shunt motor |
| B. | synchronous motor |
| C. | induction regulator |
| D. | synchronous generator |
| Answer» D. synchronous generator | |
| 35. |
In a mercury pool rectifier, the voltage drop across its electrodes___________? |
| A. | is directly proportional to load |
| B. | is inversely proportional to load |
| C. | varies exponentially with the load current |
| D. | is almost independent of load current |
| Answer» E. | |
| 36. |
In a mercury arc rectifier, the anode is usually made of_____________? |
| A. | copper |
| B. | aluminium |
| C. | silver |
| D. | graphite |
| E. | tungsten |
| Answer» E. tungsten | |
| 37. |
In a mercury arc rectifier characteristic blue luminosity is due to_____________? |
| A. | colour of mercury |
| B. | ionization |
| C. | high temperature |
| D. | electron streams |
| Answer» C. high temperature | |
| 38. |
In a mercury arc rectifier________ flow from anode to cathode |
| A. | ions |
| B. | electrons |
| C. | ions and electrons |
| D. | any of the above |
| Answer» B. electrons | |
| 39. |
In a mercury arc rectifier positive ions are attracted towards______________? |
| A. | anode |
| B. | cathode |
| C. | shell bottom |
| D. | mercury pool |
| Answer» C. shell bottom | |
| 40. |
In a glass bulb mercury arc rectifier the maximum current rating is restricted to___________? |
| A. | 2000 A |
| B. | 1500 A |
| C. | 1000 A |
| D. | 500 A |
| Answer» E. | |
| 41. |
If cathode and anode connections in a mercury arc rectifier are inter changed_____________? |
| A. | the rectifier will not operate |
| B. | internal losses will be reduced |
| C. | both ion and electron streams will move in the same direction |
| D. | the rectifier will operate at reduced efficiency |
| Answer» B. internal losses will be reduced | |
| 42. |
Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of _____________? |
| A. | 100 A at 100 V |
| B. | 200 A at 200 V |
| C. | 300 A at 300 V |
| D. | 400 A at 400 V |
| E. | 500 A at 500 V |
| Answer» F. | |
| 43. |
Copper oxide rectifier is usually designed not to operate above___________? |
| A. | 10°C |
| B. | 20°C |
| C. | 30°C |
| D. | 45°C |
| Answer» E. | |
| 44. |
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» B. 15 to 20 per cent | |
| 45. |
A synchronous converter can be started______________? |
| A. | by means of a small auxiliary motor |
| B. | from AC. side as induction motor |
| C. | from D.C. side as D.C. motor |
| D. | any of the above methods |
| E. | none of the above methods |
| Answer» E. none of the above methods | |
| 46. |
A rotary converter operates at a______________? |
| A. | low power factor |
| B. | high power factor |
| C. | zero power factor |
| D. | none of the above |
| Answer» C. zero power factor | |
| 47. |
A rotary converter is a single machine with______________? |
| A. | one armature and one field |
| B. | two armatures and one field |
| C. | one armature and two fields |
| D. | none of the above |
| Answer» B. two armatures and one field | |
| 48. |
A rotary converter in general construction and design, is more or less like___________? |
| A. | a transformer |
| B. | an induction motor |
| C. | an alternator |
| D. | any D.C. machine |
| Answer» E. | |
| 49. |
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» C. a D.C. series motor and a D.C. generator | |
| 50. |
A mercury arc rectifier possesses __________ regulation characteristics |
| A. | straight line |
| B. | curved line |
| C. | exponential |
| D. | none of the above |
| Answer» E. | |