MCQOPTIONS
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MCQOPTIONS
This section includes 657 Mcqs, each offering curated multiple-choice questions to sharpen your Testing Subject knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
At start the rotor power factor is |
| A. | very high |
| B. | very low |
| C. | unity |
| D. | zero |
| Answer» C. unity | |
| 2. |
The function of starter is |
| A. | to start the motor |
| B. | to start and stop the motor |
| C. | to limit the starting current |
| D. | to limit the applied the voltage |
| Answer» D. to limit the applied the voltage | |
| 3. |
Under running condition , the rotor resistance is proportional to |
| A. | induced emf |
| B. | rotor current |
| C. | slip |
| D. | none of these |
| Answer» E. | |
| 4. |
Under running condition, the rotor reactance is proportional to |
| A. | induced emf |
| B. | rotor current |
| C. | slip |
| D. | supply voltage |
| Answer» D. supply voltage | |
| 5. |
At start , the slip of induction motor is |
| A. | zero |
| B. | 0.5 |
| C. | one |
| D. | infinite |
| Answer» D. infinite | |
| 6. |
Maximum torque during running condition developed by three phase induction motor can be obtained by changing rotor resistance |
| A. | in squirrel cage type motor |
| B. | in slip ring type motor |
| C. | in both 1 and 2 |
| D. | none of these |
| Answer» C. in both 1 and 2 | |
| 7. |
When load is placed in three phase induction motor, its torque |
| A. | decreases |
| B. | increases |
| C. | remains unchanged |
| D. | becomes zero |
| Answer» C. remains unchanged | |
| 8. |
When load is placed in three phase induction motor its current |
| A. | decreases |
| B. | increases |
| C. | remains unchanged |
| D. | becomes zero |
| Answer» C. remains unchanged | |
| 9. |
When load is connected to three phase induction motor is increased, then its rotor induced emf |
| A. | decreases |
| B. | increases |
| C. | remains unchanged |
| D. | becomes zero |
| Answer» C. remains unchanged | |
| 10. |
When load is connected to three phase induction motor is increased, then its slip |
| A. | decreases |
| B. | increases |
| C. | remains unchanged |
| D. | becomes zero |
| Answer» C. remains unchanged | |
| 11. |
The torque developed by three phase induction motor depends on following three factors |
| A. | speed, frequency, number of poles |
| B. | voltage, current and stator impedance |
| C. | synchronous speed, rotor speed and frequency |
| D. | rotor emf, rotor current and rotor p.f |
| Answer» E. | |
| 12. |
The power factor of induction motor is during running condition |
| A. | depend on slip |
| B. | is independent of slip |
| C. | rotor reactance |
| D. | both b and c |
| Answer» E. | |
| 13. |
Torque developed by three phase induction motor |
| A. | depends on power factor of rotor |
| B. | depends on power factor of stator |
| C. | does not depend on on power factor of rotor or stator |
| D. | both 1 and 2 |
| Answer» E. | |
| 14. |
Starting torque depends on |
| A. | rotor resistance and rotor reactance during starting |
| B. | supply voltage |
| C. | both 1 and 2 |
| D. | none of these |
| Answer» D. none of these | |
| 15. |
Condition for maximum torque developed during running by a three phase induction motor is |
| A. | r2 = x2 |
| B. | r2 =s x2 |
| C. | r2 /s x2 |
| D. | x2/r2 |
| Answer» C. r2 /s x2 | |
| 16. |
Condition for maximum torque developed during starting by a three phase induction motor is |
| A. | r2 = x2 |
| B. | r2 =s x2 |
| C. | r2 /s x2 |
| D. | x2/r2 |
| Answer» B. r2 =s x2 | |
| 17. |
The torque developed by a 3-phase induction motor during starting |
| A. | depends on rotor induced emf during starting |
| B. | rotor induced emf during running condition |
| C. | does not depend on rotor induced emf |
| D. | none of these |
| Answer» B. rotor induced emf during running condition | |
| 18. |
High starting torque can be produced by induction motor if |
| A. | a squirrel cage motor is started with auto-transformer starter |
| B. | a slip-ring induction motor is started with star-delta starter |
| C. | a squirrel cage motor is started by direct-on-line starter. |
| D. | a slip-ring induction motor is started with rotor resistance starter |
| Answer» E. | |
| 19. |
A squirrel cage induction motor is favoured when ……………….. is the main consideration. |
| A. | initial cost |
| B. | rotor core and rotor teeth |
| C. | stator core and stator teeth |
| D. | stator winding |
| Answer» D. stator winding | |
| 20. |
An induction motor employs a starting device to restrict………….. at start |
| A. | line voltage |
| B. | line current |
| C. | torque |
| D. | power |
| Answer» C. torque | |
| 21. |
In a 3-phase induction motor, the mechanical power developed, in terms of air rotor input P2 is |
| A. | (s - 1) p2 |
| B. | p2 / (1-s) |
| C. | 1/(s p2) |
| D. | (1 - s) p2 |
| Answer» E. | |
| 22. |
When quick speed reversal is a consideration, the motor preffered is |
| A. | synchronous motor |
| B. | squirrel cage induction motor |
| C. | wound rotor induction motor |
| D. | dc motor |
| Answer» E. | |
| 23. |
The only disadvantage of field control method for controlling the speed of a dc shunt motor is that it |
| A. | gives speeds lower than the normal speed |
| B. | is wasteful |
| C. | needs a large rheostat |
| D. | adversely affects commutation |
| Answer» E. | |
| 24. |
Motor starters are essential for |
| A. | accelerating the motor |
| B. | starting the motor |
| C. | avoiding excessive starting current |
| D. | preventing fuse blowing |
| Answer» D. preventing fuse blowing | |
| 25. |
By putting controller resistance in series with the armature of a DC motor, we can obtain speeds |
| A. | above the normal speed only |
| B. | below the normal speed only |
| C. | above as well as below the normal speed |
| D. | none of the above |
| Answer» C. above as well as below the normal speed | |
| 26. |
By flux control method of speed control of a dc shunt motor, we can obtain speeds. |
| A. | above the normal speed only |
| B. | below the normal speed only |
| C. | above as well as below the normal speed |
| D. | none of the above |
| Answer» B. below the normal speed only | |
| 27. |
A 20HP DC motor has 89.3% efficiency at rated power. What are its total losses? |
| A. | 1787w |
| B. | 1232w |
| C. | 2184w |
| D. | 1572w |
| Answer» B. 1232w | |
| 28. |
A DC shunt motor is rotating at 267 rad/sec and developing 57.2Nm of torque. How many kilowatts of mechanical power are developed? |
| A. | 9.8kw |
| B. | 15.3kw |
| C. | 17.8kw |
| D. | 11.2kw |
| Answer» C. 17.8kw | |
| 29. |
In a DC compound machine, |
| A. | shunt field winding plays dominent role |
| B. | series field winding plays dominent role |
| C. | either can play dominent role |
| D. | both play equally dominent role |
| Answer» B. series field winding plays dominent role | |
| 30. |
A DC motor runs at 1725rpm at full load and 1775rpm at no load. The speed regulation is _____. |
| A. | 0.047 |
| B. | 0.029 |
| C. | 0.076 |
| D. | 0.015 |
| Answer» C. 0.076 | |
| 31. |
Which motor should not be used for centrifugal pumps? |
| A. | shunt |
| B. | series |
| C. | cumulatively compound |
| D. | differenctially compound |
| Answer» C. cumulatively compound | |
| 32. |
The armature torque of a DC motor running of 800rpm is 99.3Nm and shaft torque is 93.3Nm. The iron and friction losses are__. |
| A. | 502w |
| B. | 400w |
| C. | 200w |
| D. | 300w |
| Answer» B. 400w | |
| 33. |
If the applied voltage to a DC machine is 230V, then back emf for maximum power developed is ___. |
| A. | 200v |
| B. | 230v |
| C. | 115v |
| D. | 460v |
| Answer» D. 460v | |
| 34. |
A 440V shunt motor has an armature resistance of 0.8Ω field reistnace of 200Ω . Find the back emf when giving an output of 7.46kW at 85 % efficiency? |
| A. | 222.4v |
| B. | 425.8v |
| C. | 312.6v |
| D. | 392.7v |
| Answer» C. 312.6v | |
| 35. |
The friction and windage losses in a DC motor depends upon ____. |
| A. | speed |
| B. | flux |
| C. | armature current |
| D. | field and armature resistance |
| Answer» B. flux | |
| 36. |
The most suitable motor for elevators is the ___ motor. |
| A. | series |
| B. | shunt |
| C. | differential compound |
| D. | cumulative compound |
| Answer» E. | |
| 37. |
In a vaccum cleaner, we generally use ____ motor |
| A. | shunt |
| B. | cumulative - compound |
| C. | series motor |
| D. | differetial compounded |
| Answer» D. differetial compounded | |
| 38. |
A motor takes a large starting currents because _____. |
| A. | the armature resistance is high |
| B. | back emf is low |
| C. | shunt field is produce weak field |
| D. | none of the above |
| Answer» C. shunt field is produce weak field | |
| 39. |
____ motor is most suitable for punch presses |
| A. | shunt |
| B. | series |
| C. | differential compound |
| D. | cumulative compound |
| Answer» E. | |
| 40. |
A DC series motor is most suitable for _____. |
| A. | cranes |
| B. | pump |
| C. | lathes |
| D. | punch presses |
| Answer» B. pump | |
| 41. |
A DC motor develops torque of the 100Nm at 400 rpm, at 300 rpm a motor will develop torque of___. |
| A. | 133nm |
| B. | 100nm |
| C. | 67nm |
| D. | 180nm |
| Answer» C. 67nm | |
| 42. |
Back EMF of DC motor depends on |
| A. | field flux |
| B. | shape of conductor |
| C. | type of sliprings |
| D. | brush material |
| Answer» B. shape of conductor | |
| 43. |
If the applied voltage of dc motor is reduced to half with load torque doubled the armature current will be____ |
| A. | unaltered |
| B. | zero |
| C. | doubled |
| D. | half |
| Answer» D. half | |
| 44. |
In a 4 pole machine___ |
| A. | alternate poles are north and south |
| B. | two north poles follow two south poles |
| C. | in all there are north poles |
| D. | in all there are south poles |
| Answer» B. two north poles follow two south poles | |
| 45. |
____ motors never use belt- connected loads. |
| A. | series |
| B. | shunt |
| C. | cumulatively compounded |
| D. | differential compound |
| Answer» B. shunt | |
| 46. |
Cumulatively compounded motors are used where we require _____. |
| A. | variable speed |
| B. | poor speed regulation |
| C. | sudden heavy loads for short duration |
| D. | none of the above |
| Answer» D. none of the above | |
| 47. |
DC series motor are used in those applications where ____ is required. |
| A. | high statring torque |
| B. | constant speed |
| C. | low no load speed |
| D. | none of the above |
| Answer» B. constant speed | |
| 48. |
A series motor will over speed when ____. |
| A. | the load is increased |
| B. | the field is opened |
| C. | the armature circuit is opened |
| D. | laod is removed |
| Answer» E. | |
| 49. |
DC shunt motor are used in those applications where____ is required. |
| A. | high statring torque |
| B. | practically constant speed |
| C. | high no load speed |
| D. | variable speed |
| Answer» C. high no load speed | |
| 50. |
____ motor has the best speed regulation |
| A. | series |
| B. | cumulatively compounded |
| C. | shunt |
| D. | differentially compounded |
| Answer» D. differentially compounded | |