MCQOPTIONS
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MCQOPTIONS
This section includes 121 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.
| 51. |
In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when_______________? |
| A. | there is no load on|he generator |
| B. | the generator runs on full load |
| C. | the generator runs on overload |
| D. | the generator runs on designed speed |
| Answer» B. the generator runs on full load | |
| 52. |
A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly_______________? |
| A. | 150 V |
| B. | 175 V |
| C. | 240 V |
| D. | 290 V |
| Answer» D. 290 V | |
| 53. |
A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be_____________? |
| A. | zero |
| B. | about 2 V |
| C. | about 50 V |
| D. | 220 V |
| Answer» C. about 50 V | |
| 54. |
The purpose of providing dummy coils in a generator is__________________? |
| A. | to reduce eddy current losses |
| B. | to enhance flux density |
| C. | to amplify voltage |
| D. | to provide mechanical balance for the rotor |
| Answer» E. | |
| 55. |
The e.m.f. generated in a D.C. generator is directly proportional to____________? |
| A. | flux/pole |
| B. | speed of armature |
| C. | number of poles |
| D. | all of the above |
| Answer» C. number of poles | |
| 56. |
If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be____________? |
| A. | zero |
| B. | small |
| C. | the same as rated voltage |
| D. | high |
| Answer» B. small | |
| 57. |
Armature reaction in a generator results in_____________? |
| A. | demagnetisation of leading pole tip and magnetisation of trailing pole tip |
| B. | demagnetisation of trailing pole tip and magnetisation of leading pole tip |
| C. | damagnetising the center of all poles |
| D. | magnetising the center of all poles |
| Answer» B. demagnetisation of trailing pole tip and magnetisation of leading pole tip | |
| 58. |
In a D.C. generator the critical resistance can be increased by_____________? |
| A. | increasing its field resistance |
| B. | decreasing its field resistance |
| C. | increasing its speed |
| D. | decreasing its speed |
| Answer» D. decreasing its speed | |
| 59. |
Which generator would you prefer for feeding long D.C. transmission lines ? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Over compound generator |
| D. | Flat compound generator |
| Answer» D. Flat compound generator | |
| 60. |
Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure. |
| A. | Series field |
| B. | Compensating field |
| C. | Inter pole field |
| D. | Shunt field |
| Answer» E. | |
| 61. |
In over compounded generator, full load terminal voltage is______________? |
| A. | almost zero |
| B. | less than no load terminal voltage |
| C. | more than no load terminal voltage |
| D. | equal to no-load terminal voltage |
| Answer» D. equal to no-load terminal voltage | |
| 62. |
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except______________? |
| A. | interpoles |
| B. | dummy coils |
| C. | compensating winding |
| D. | shifting of axis of brushes |
| Answer» C. compensating winding | |
| 63. |
If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to______________? |
| A. | reverse the field connections |
| B. | increase the field resistance |
| C. | increase the speed of primemover |
| D. | check armature insulation resistance |
| Answer» B. increase the field resistance | |
| 64. |
Wave winding is composed of_______________? |
| A. | any even number of conductors |
| B. | any odd number of conductors |
| C. | that even number which is exact multiple of poles + 2 |
| D. | that even number which is exact multiple of poles |
| Answer» D. that even number which is exact multiple of poles | |
| 65. |
In a level compounded D.C. generator, full load terminal voltage is______________? |
| A. | negligibly low |
| B. | equal to no-load terminal voltage |
| C. | more than no-load terminal voltage |
| D. | less than no-load terminal voltage |
| Answer» C. more than no-load terminal voltage | |
| 66. |
For both lap and wave windings, there are as many commutator bars as the number of_____________? |
| A. | slots |
| B. | armature conductors |
| C. | winding elements |
| D. | poles |
| Answer» D. poles | |
| 67. |
As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately______________? |
| A. | 40 percent |
| B. | 25 percent |
| C. | 10 percent |
| D. | 5 percent |
| Answer» E. | |
| 68. |
The series field of a short-shunt D.C. generator is excited by_______________? |
| A. | external current |
| B. | armature current |
| C. | shunt current |
| D. | load current |
| Answer» E. | |
| 69. |
In a separately excited generator supplying rated load the armature reaction. |
| A. | is always present |
| B. | is always absent |
| C. | may be sometimes present |
| D. | none of the above |
| Answer» B. is always absent | |
| 70. |
When two D.C. series generators are running in parallel, an equilizer bar is used________________? |
| A. | to increase the speed and hence generated e.m.f. |
| B. | to increase the series flux |
| C. | so that two similar machines will pass approximately equal currents to the load |
| D. | to reduce the combined effect of ar-mature reaction of both machines |
| Answer» D. to reduce the combined effect of ar-mature reaction of both machines | |
| 71. |
The critical resistance of the D.C. generator is the resistance of_____________? |
| A. | field |
| B. | brushes |
| C. | armature |
| D. | load |
| Answer» B. brushes | |
| 72. |
In D.C. generators on no-load, the air gap flux distribution in space is______________? |
| A. | sinusoidal |
| B. | triangular |
| C. | pulsating |
| D. | flat topped |
| Answer» E. | |
| 73. |
Shunt generators are most suited for stable parallel operation because of their______________? |
| A. | rising voltage characteristics |
| B. | identical voltage characteristics |
| C. | drooping voltage characteristics |
| D. | linear voltage characteristics |
| Answer» D. linear voltage characteristics | |
| 74. |
The purpose of providing dummy coils in a generator is____________? |
| A. | to reduce eddy current losses |
| B. | to enhance flux density |
| C. | to amplify voltage |
| D. | to provide mechanical balance for the rotor |
| Answer» E. | |
| 75. |
The main factor which leads to unstable parallel operation of flat and over compounded generators is_____________? |
| A. | their rising voltage characteristics |
| B. | unequal number of turns in their series field windings |
| C. | unequal speed regulation of their primemovers |
| D. | unequal series field resistances |
| Answer» B. unequal number of turns in their series field windings | |
| 76. |
In a D.C. machine stray loss is the sum of_____________? |
| A. | total copper loss and mechanical loss |
| B. | armature copper loss and iron loss |
| C. | shunt field copper loss and mechanical loss |
| D. | iron loss and mechanical loss |
| Answer» E. | |
| 77. |
The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except:_____________? |
| A. | armature reaction |
| B. | armature resistance drop |
| C. | field weakening due to armature reaction and armature |
| D. | commutation |
| Answer» E. | |
| 78. |
The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________? |
| A. | 640 V |
| B. | 620 V |
| C. | 600 V |
| D. | 580 V |
| Answer» E. | |
| 79. |
A D.C. welding generator has____________? |
| A. | lap winding |
| B. | wave moving |
| C. | duplex winding |
| D. | any of the above |
| Answer» B. wave moving | |
| 80. |
In a D.C. generator the critical resistance refers to the resistance of_____________? |
| A. | brushes |
| B. | field |
| C. | armature |
| D. | load |
| Answer» C. armature | |
| 81. |
Which of the following statement about D.C. generators is false ? |
| A. | Compensating winding in a D.C. machine helps in commutation |
| B. | In a D. C. generator interpoles winding is connected in series with the armature winding |
| C. | Back pitch and front pitch are both odd and approximately equal to the pole pitch |
| D. | Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators |
| Answer» E. | |
| 82. |
Armature coil is short circuited by brushes when it lies_____________? |
| A. | along neutral axis |
| B. | along field axis |
| C. | in any of the above positions |
| D. | in none of the above positions |
| Answer» B. along field axis | |
| 83. |
To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them? |
| A. | just ahead of magnetic neutral axis |
| B. | in magnetic neutral axis |
| C. | just behind the magnetic neutral axis |
| D. | none |
| Answer» B. in magnetic neutral axis | |
| 84. |
A cumulatively compounded long shunt generator when operating as a motor would be____________? |
| A. | cumulatively compounded long shunt |
| B. | deferentially compounded long shunt |
| C. | cumulatively compounded short shunt |
| D. | differentially compounded short shunt |
| Answer» C. cumulatively compounded short shunt | |
| 85. |
The demagnetising component of armature reaction in a D.C. generator___________? |
| A. | reduces generator e.m.f. |
| B. | increases armature speed |
| C. | reduces interpoles flux density |
| D. | results in sparking trouble |
| Answer» B. increases armature speed | |
| 86. |
Magnetic field in a D.C. generator is produced by_______________? |
| A. | electromagnets |
| B. | permanent magnets |
| C. | both A. and B. |
| D. | none of the above |
| Answer» B. permanent magnets | |
| 87. |
To avoid formation of grooves in the commutator of a D.C. machine? |
| A. | the brushes of opposite polarity should track each other |
| B. | the brushes of same polarity should track each other |
| C. | brush position has no effect on the commutator grooving |
| D. | None |
| Answer» B. the brushes of same polarity should track each other | |
| 88. |
The number of brushes in a commutator depends on______________? |
| A. | speed of armature |
| B. | type of winding |
| C. | voltage |
| D. | amount of current to be collected |
| Answer» E. | |
| 89. |
The rapid wear of brushes takes place due to____________? |
| A. | abrasion from dust |
| B. | excessive spring pressure |
| C. | rough commutator bars |
| D. | high mica insulation between com-mutation bars |
| E. | all of the above factors |
| Answer» F. | |
| 90. |
Compensating windings are used in D.C. generators______________? |
| A. | mainly to reduce the eddy currents by providing local short-circuits |
| B. | to provide path for the circulation of cooling air |
| C. | to neutralise the cross-magnetising effect of the armature reaction |
| D. | none of the above |
| Answer» D. none of the above | |
| 91. |
The following constitute short-circuit in the armature winding. |
| A. | Insulation failure between two commutator bars |
| B. | Insulation failure between two turns of a coil |
| C. | Two of more turns of the same coil getting grounded |
| D. | All of the above |
| Answer» E. | |
| 92. |
The voltage drop for which of the following types of brush can be expected to be least ? |
| A. | Graphite brushes |
| B. | Carbon brushes |
| C. | Metal graphite brushes |
| D. | None of the above |
| Answer» D. None of the above | |
| 93. |
In D.C. generators, lap winding is used for______________? |
| A. | high voltage, high current |
| B. | low voltage, high current |
| C. | high voltage, low current |
| D. | low voltage, low current |
| Answer» C. high voltage, low current | |
| 94. |
In a D.C. generator the ripples in the direct e.m.f. generated are reduced by_____________? |
| A. | using conductor of annealed copper |
| B. | using commutator with large number of segments |
| C. | using carbon brushes of superior quality |
| D. | using equiliser rings |
| Answer» D. using equiliser rings | |
| 95. |
Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be_______________? |
| A. | 2 : 3 |
| B. | 3 : 1 |
| C. | 3 : 2 |
| D. | 1 : 3 |
| Answer» C. 3 : 2 | |
| 96. |
Number of tappings for each equalizer ring is equal to_____________? |
| A. | number of pole pairs |
| B. | number of poles |
| C. | number of parallel paths |
| D. | number of commutator segments |
| Answer» B. number of poles | |
| 97. |
A series generator can self-excite:______________? |
| A. | only if the load current is zero |
| B. | only if the load current is not zero |
| C. | irrespective of the value of load current |
| D. | none of the above |
| Answer» C. irrespective of the value of load current | |
| 98. |
The armature core of a D.C. generator is usually made of__________________? |
| A. | silicon steel |
| B. | copper |
| C. | non-ferrous material |
| D. | cast-iron |
| Answer» B. copper | |
| 99. |
A D.C. generator can be considered as____________? |
| A. | rectifier |
| B. | primemover |
| C. | rotating amplifier |
| D. | power pump |
| Answer» D. power pump | |
| 100. |
In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilized is called____________? |
| A. | rotor |
| B. | stator |
| C. | field |
| D. | armature |
| Answer» E. | |