MCQOPTIONS
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MCQOPTIONS
This section includes 98 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 the D.C. motor the iron losses occur in____________? |
| A. | the field |
| B. | the armature |
| C. | the brushes |
| D. | the commutator |
| Answer» C. the brushes | |
| 52. |
In D.C. shunt motors as load is reduced__________________? |
| A. | the speed will increase abruptly |
| B. | the speed will increase in proportion to reduction in load |
| C. | the speed will remain almost/constant |
| D. | the speed will reduce |
| Answer» D. the speed will reduce | |
| 53. |
In D.C. machines the residual magnetism is of the order of_________________? |
| A. | 2 to 3 per cent |
| B. | 10 to 15 per cent |
| C. | 20 to 25 per cent |
| D. | 50 to 75 per cent |
| Answer» B. 10 to 15 per cent | |
| 54. |
In D.C. machines fractional pitch winding is used__________? |
| A. | to improve cooling |
| B. | to reduce copper losses |
| C. | to increase the generated e.m.f. |
| D. | to reduce the sparking |
| Answer» E. | |
| 55. |
In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________? |
| A. | 100% |
| B. | around 90% |
| C. | anywhere between 75% and 90% |
| D. | less than 50% |
| Answer» E. | |
| 56. |
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because____________? |
| A. | back e.m.f. is equal to armature drop |
| B. | armature drop is negligible |
| C. | flux is proportional to armature current |
| D. | flux is practically constant in D:C. shunt motors |
| Answer» E. | |
| 57. |
In case of conductively compensated D.C. series motors, the compensating winding is provided______________? |
| A. | as separately wound unit |
| B. | in parallel with armature winding |
| C. | in series with armature winding |
| D. | in parallel with field winding |
| Answer» D. in parallel with field winding | |
| 58. |
In a manual shunt motor starter? |
| A. | over load relay is connected in series and no volt relay in parallel with the load |
| B. | over load relay is connected in parallel and no volt relay in series with the load |
| C. | over load relay and no volt relay are both connected in series with the load |
| D. | over load relay and no volt relay are both connected in parallel with the load |
| Answer» B. over load relay is connected in parallel and no volt relay in series with the load | |
| 59. |
In a differentially compounded D.C. motor, if shunt field suddenly opens____________? |
| A. | the motor will first stop and then run in opposite direction as series motor |
| B. | the motor will work as series motor and run at slow speed in the same direction |
| C. | the motor will work as series motor and run at high speed in the same direction |
| D. | the motor will not work and come to stop |
| Answer» B. the motor will work as series motor and run at slow speed in the same direction | |
| 60. |
In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be_____________? |
| A. | almost negligible |
| B. | rated full-load current |
| C. | less than full-load current |
| D. | more than full-load current |
| Answer» E. | |
| 61. |
In a D.C. shunt motor, speed is______________? |
| A. | independent of armature current |
| B. | directly proportional to the armature current |
| C. | proportional to the square of the current |
| D. | inversely proportional to the armature current |
| Answer» B. directly proportional to the armature current | |
| 62. |
In a DC motor the inter-pole winding is connected in________________? |
| A. | series with field winding |
| B. | series speed armature winding |
| C. | parallel big field winding |
| D. | parallel with armature winding |
| Answer» C. parallel big field winding | |
| 63. |
In a D.C. generator, the iron losses mainly take place in___________ |
| A. | yoke |
| B. | commutator |
| C. | armature conductors |
| D. | armature rotor |
| Answer» E. | |
| 64. |
In a D.C. generator all of the following could be the effects of iron losses except___________? |
| A. | Loss of efficiency |
| B. | Excessive heating of core |
| C. | Increase in terminal voltage |
| D. | Rise in temperature of ventilating air |
| Answer» D. Rise in temperature of ventilating air | |
| 65. |
If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking? |
| A. | regenerative |
| B. | plugging |
| C. | dynamic braking |
| D. | none of the above |
| E. | any of the above |
| Answer» C. dynamic braking | |
| 66. |
If the supply voltage for a D.C. motor is increased, which of the following will decrease ? |
| A. | Starting torque |
| B. | Operating speed |
| C. | Full-load current |
| D. | All of the above |
| Answer» D. All of the above | |
| 67. |
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will_________? |
| A. | increase |
| B. | decrease |
| C. | remain same |
| D. | become zero |
| Answer» B. decrease | |
| 68. |
If the load on a DC shunt motor is increases, its speed is slightly reduced due to______________? |
| A. | increase in armature current |
| B. | increase in flux |
| C. | decrease in reactance |
| D. | decrease in back emf |
| Answer» E. | |
| 69. |
If the field winding resistance of a DC shunt motor is increases, its speed will____________? |
| A. | decreases |
| B. | increases |
| C. | remains same |
| D. | none of the above |
| Answer» C. remains same | |
| 70. |
If the field of a D.C. shunt motor gets opened while motor is running______________? |
| A. | the speed of motor will be reduced % |
| B. | the armature current will reduce |
| C. | the motor will attain dangerously high speed 1 |
| D. | the motor will continue to nuvat constant speed |
| Answer» D. the motor will continue to nuvat constant speed | |
| 71. |
If I2 be the armature current, then speed of a D.C. shunt motor is_______________? |
| A. | independent of Ia |
| B. | proportional to la |
| C. | varies as (Ia) |
| D. | varies as la |
| Answer» B. proportional to la | |
| 72. |
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens__________? |
| A. | nothing will happen to the motor |
| B. | this will make armature to take heavy current, possibly burning it |
| C. | this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| D. | motor will run at very slow speed |
| Answer» D. motor will run at very slow speed | |
| 73. |
If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________? |
| A. | this will make armature to take heavy current, possibly burning it |
| B. | this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses |
| C. | nothing will happen to motor |
| D. | motor will come to stop |
| Answer» B. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses | |
| 74. |
If a D.C. motor is connected across the A.C. supply it will_______________? |
| A. | run at normal speed |
| B. | not run |
| C. | run at lower speed |
| D. | burn due to heat produced in the field winding by .eddy currents |
| Answer» E. | |
| 75. |
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor_____________? |
| A. | of lower H.P. should be selected |
| B. | of higher H.P. should be selected |
| C. | can be used for 50°C ambient temperature also |
| D. | is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor |
| Answer» E. | |
| 76. |
Hopkinson’s test on D.C. machines is conducted at_______________? |
| A. | no-load |
| B. | part load |
| C. | full-load |
| D. | overload |
| Answer» D. overload | |
| 77. |
For the same H.P. rating and full load speed, following motor has poor starting torque_____________? |
| A. | shunt |
| B. | series |
| C. | differentially compounded |
| D. | cumulativelyc’ompounded |
| Answer» D. cumulativelyc’ompounded | |
| 78. |
For starting a D.C. motor a starter is required because___________? |
| A. | it limits the speed of the motor |
| B. | it limits the starting current to a safe value |
| C. | it starts the motor |
| D. | none of the above |
| Answer» C. it starts the motor | |
| 79. |
For a D.C. shunt motor if the excitation is changed_______________? |
| A. | torque will remain constant |
| B. | torque will change but power will remain constant |
| C. | torque and power both will change |
| D. | torque, power and speed, all will change |
| Answer» C. torque and power both will change | |
| 80. |
Following motor is used where high starting torque and wide speed range control is required? |
| A. | Single phase capacitor start |
| B. | Induction motor |
| C. | Synchronous motor |
| D. | D.C. motor |
| E. | None of the above |
| Answer» E. None of the above | |
| 81. |
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor, compound motor will have to be_____________? |
| A. | level compounded |
| B. | under compounded |
| C. | cumulatively compounded |
| D. | differentially compounded |
| Answer» D. differentially compounded | |
| 82. |
During rheostat braking of D.C. series motors_____________? |
| A. | motor is run as a generator |
| B. | motor is reversed in direction |
| C. | motor is run at reduced speed |
| Answer» B. motor is reversed in direction | |
| 83. |
Differentially compound D.C. motors can find applications requiring___________? |
| A. | high starting torque |
| B. | low starting torque |
| C. | variable speed |
| D. | frequent on-off cycles |
| Answer» C. variable speed | |
| 84. |
D.C. shunt motors are used for driving____________? |
| A. | trains |
| B. | cranes |
| C. | hoists |
| D. | machine tools |
| Answer» E. | |
| 85. |
D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________? |
| A. | series motor |
| B. | shunt motor |
| C. | compound motor |
| D. | any of the above |
| Answer» B. shunt motor | |
| 86. |
D.C. series motors are used______________? |
| A. | where load is constant |
| B. | where load changes frequently |
| C. | where constant operating speed is needed |
| D. | in none of the above situations |
| Answer» E. | |
| 87. |
D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this______________? |
| A. | series motor |
| B. | shunt motor |
| C. | compound motor |
| D. | any of the above |
| Answer» D. any of the above | |
| 88. |
D.C. generators are normally designed for maximum efficiency around_____________? |
| A. | full-load |
| B. | rated r.p.m |
| C. | rated voltage |
| D. | all of the above |
| Answer» B. rated r.p.m | |
| 89. |
D.C. generators are installed near the load centres to reduce_____________? |
| A. | iron losses |
| B. | line losses |
| C. | sparking |
| D. | corona losses |
| Answer» C. sparking | |
| 90. |
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of_____________? |
| A. | D.C. series motor |
| B. | D.C. shunt motor |
| C. | induction motor |
| D. | all of above motors |
| Answer» B. D.C. shunt motor | |
| 91. |
As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuit____________________? |
| A. | a resistance is connected in series with armature |
| B. | a resistance is connected parallel to the armature |
| C. | armature is temporarily open circuited |
| D. | a high value resistor is connected across the field winding |
| Answer» B. a resistance is connected parallel to the armature | |
| 92. |
As -the load is increased the speed of D.C. shunt motor will____________? |
| A. | reduce slightly |
| B. | increase slightly |
| C. | increase proportionately |
| D. | remains unchanged |
| Answer» B. increase slightly | |
| 93. |
Armature reaction in dc motor results___________? |
| A. | decrease in speed |
| B. | increase in speed |
| C. | short circuit |
| D. | open circuit |
| Answer» C. short circuit | |
| 94. |
According to Fleming’s left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of_________________? |
| A. | current in the conductor aovtaat of conductor |
| B. | resultant force on conductor |
| C. | none of the above |
| Answer» B. resultant force on conductor | |
| 95. |
A three point starter is considered suitable for______________? |
| A. | shunt motors |
| B. | shunt as well as compound motors |
| C. | shunt, compound and series motors |
| D. | all D.C. motors |
| Answer» C. shunt, compound and series motors | |
| 96. |
A direct on line starter is used: for starting motors___________? |
| A. | up to 5 H.P |
| B. | up to 10 H.P |
| C. | up to 15 H.P |
| D. | up to 20 H.P |
| Answer» B. up to 10 H.P | |
| 97. |
A dc series motor should not be started on no load because it would___________? |
| A. | not develop starting torque |
| B. | fail to start without load |
| C. | run at dangerously high speed |
| D. | draw more current without producing sufficient torque |
| Answer» D. draw more current without producing sufficient torque | |
| 98. |
A D.C. series motor is that which______________? |
| A. | has its field winding consisting of thick wire and less turns |
| B. | has a poor torque |
| C. | can be started easily without load |
| D. | has almost constant speed |
| Answer» B. has a poor torque | |