MCQOPTIONS
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MCQOPTIONS
This section includes 76 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
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 | |
| 52. |
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» E. | |
| 53. |
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 | |
| 54. |
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 'C. machine |
| Answer» E. | |
| 55. |
The ignited or auxiliary anode in mercury arc rectifier is made of |
| A. | Graphite |
| B. | Boron carbide |
| C. | Aluminium |
| D. | Copper |
| Answer» C. Aluminium | |
| 56. |
In which of the following appUcations, direct current is absolutely essential ? |
| A. | Illumination |
| B. | Electrolysis |
| C. | Variable speed operation |
| D. | Traction |
| Answer» C. Variable speed operation | |
| 57. |
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 | |
| 58. |
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. | |
| 59. |
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. | |
| 60. |
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 | |
| 61. |
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. | |
| 62. |
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 | |
| 63. |
Which of the following AC. motors is usually used in large motor-generator sets? |
| A. | Synchronous motor |
| B. | Squirrel cage induction motor |
| C. | Slip ring induction motor |
| D. | Any of the above |
| Answer» B. Squirrel cage induction motor | |
| 64. |
In a mercury arc rectifier positive ions are attracted towards |
| A. | anode |
| B. | cathode |
| C. | shell bottom |
| D. | mercury pool |
| Answer» C. shell bottom | |
| 65. |
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 | |
| 66. |
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. | |
| 67. |
The metal rectifiers, as compared to mercury arc rectifiers |
| A. | operate on low temperatures |
| B. | can operate on high voltages |
| C. | can operate on heavy loads |
| D. | give poor regulation |
| E. | none of the above |
| Answer» B. can operate on high voltages | |
| 68. |
In a mercury arc rectifier, the anode is usually made of |
| A. | copper |
| B. | aluminium |
| C. | silver |
| D. | graphite |
| E. | tungsten |
| Answer» E. tungsten | |
| 69. |
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. | |
| 70. |
In selenium rectifiers efficiencies ranging from ______ to ______ percent are attainable |
| A. | 25, 35 |
| B. | 40, 50 |
| C. | 60, 70 |
| D. | 75, 85 |
| Answer» E. | |
| 71. |
When a rectifier is loaded which of the following voltage drops take place ? |
| A. | Voltage drop in transformer reactance |
| B. | Voltage drop in resistance of transformer and smoothing chokes |
| C. | Arc voltage drop |
| D. | All of the above |
| Answer» E. | |
| 72. |
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 | |
| 73. |
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» E. | |
| 74. |
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. | |
| 75. |
Copper oxide rectifier is usually designed not to operate above |
| A. | 10°C |
| B. | 20°C |
| C. | 30°C |
| D. | 45°C |
| Answer» E. | |
| 76. |
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. | |