McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 1. |
B. DC MOTOR 1. No-load speed of which of the following motor will be highest ? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differentiate compound motor |
| Answer» B. Series motor | |
| 2. |
The direction of rotation of a D.C. series motor can be changed by |
| A. | interchanging supply terminals |
| B. | interchanging field terminals |
| C. | either of (a) and (b) above |
| D. | None of the above |
| Answer» B. interchanging field terminals | |
| 3. |
Which of the following application requires high starting torque ? |
| A. | Lathe machine |
| B. | Centrifugal pump |
| C. | Locomotive |
| D. | Air blower |
| Answer» C. Locomotive | |
| 4. |
If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Differentially compound motor |
| D. | Cumulative compound motor |
| Answer» A. Series motor | |
| 5. |
Which D.C. motor will be preferred for machine tools ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulative compound motor |
| D. | Differential compound motor |
| Answer» B. Shunt motor | |
| 6. |
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» B. low starting torque | |
| 7. |
Which D.C. motor is preferred for elevators ? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» D. Cumulative compound motor | |
| 8. |
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 |
| C. | resultant force on conductor |
| D. | none of the above |
| Answer» A. current in the conductor aovtaat of conductor | |
| 9. |
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» C. the motor will attain dangerously high speed 1 | |
| 10. |
Starters are used with D.C. motors because |
| A. | these motors have high starting torque |
| B. | these motors are not self-starting |
| C. | back e.m.f. of these motors is zero initially |
| D. | to restrict armature current as there is no back e.m.f. while starting |
| Answer» D. to restrict armature current as there is no back e.m.f. while starting | |
| 11. |
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» C. the speed will remain almost/constant | |
| 12. |
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» A. has its field winding consisting of thick wire and less turns | |
| 13. |
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» B. it limits the starting current to a safe value | |
| 14. |
The type of D.C. motor used for shears and punches is |
| A. | shunt motor |
| B. | series motor |
| C. | differential compoutid D.C. motor |
| D. | cumulative compound D.C. motor |
| Answer» D. cumulative compound D.C. motor | |
| 15. |
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» D. burn due to heat produced in the field winding by .eddy currents | |
| 16. |
To get the speed of D.C, motor below the normal without wastage of electrical energy is used. |
| A. | Ward Leonard control |
| B. | rheostatic control |
| C. | any of the above method |
| D. | none of the above method |
| Answer» A. Ward Leonard control | |
| 17. |
When two D.C. series motors are connected in parallel, the resultant speed is |
| A. | more than the normal speed |
| B. | loss than the normal speed |
| C. | normal speed |
| D. | zero |
| Answer» C. normal speed | |
| 18. |
The speed of a D.C. shunt motor more than its full-load speed can be obtained by |
| A. | decreasing the field current |
| B. | increasing the field current |
| C. | decreasing the armature current |
| D. | increasing the armature current |
| Answer» A. decreasing the field current | |
| 19. |
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» A. independent of armature current | |
| 20. |
A direct on line starter is used: for starting motors |
| A. | iip to 5 H.P. |
| B. | up to 10 H.P. |
| C. | up to 15 H.P. |
| D. | up to 20 H.P. |
| Answer» A. iip to 5 H.P. | |
| 21. |
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly? |
| A. | The motor will stop |
| B. | The motor will continue to run |
| C. | The armature may burn |
| D. | The motor will run noisy |
| Answer» C. The armature may burn | |
| 22. |
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» D. flux is practically constant in D:C. shunt motors | |
| 23. |
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» D. more than full-load current | |
| 24. |
These days D.C. motors are widely used in |
| A. | pumping sets |
| B. | air compressors |
| C. | electric traction |
| D. | machine shops |
| Answer» C. electric traction | |
| 25. |
By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor? |
| A. | Frame |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» C. Commutator | |
| 26. |
In which of the following applications D.C. series motor is invariably tried? |
| A. | Starter for a car |
| B. | Drive for a water pump |
| C. | Fan motor |
| D. | Motor operation in A.C. or D.C. |
| Answer» A. Starter for a car | |
| 27. |
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» D. to reduce the sparking | |
| 28. |
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» B. shunt as well as compound motors | |
| 29. |
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» D. less than 50% | |
| 30. |
The ratio of starting torque to full-load torque is least in case of |
| A. | series motors |
| B. | shunt motors |
| C. | compound motors |
| D. | none of the above |
| Answer» B. shunt motors | |
| 31. |
In D.C. motor which of the following can sustain the maximum temperature rise? |
| A. | Slip rings |
| B. | Commutator |
| C. | Field winding |
| D. | Armature winding |
| Answer» C. Field winding | |
| 32. |
Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ? |
| A. | Lenz's law |
| B. | Faraday's law |
| C. | Coloumb's law |
| D. | Fleming's left-hand rule |
| Answer» D. Fleming's left-hand rule | |
| 33. |
Which of the following load normally needs starting torque more than the rated torque? |
| A. | Blowers |
| B. | Conveyors |
| C. | Air compressors |
| D. | Centrifugal pumps |
| Answer» B. Conveyors | |
| 34. |
The starting resistance of a D.C. motor is generally |
| A. | low |
| B. | around 500 Q |
| C. | 1000 Q |
| D. | infinitely large |
| Answer» A. low | |
| 35. |
The speed of a D.C. series motor is |
| A. | proportional to the armature current |
| B. | proportional to the square of the armature current |
| C. | proportional to field current |
| D. | inversely proportional to the armature current |
| Answer» D. inversely proportional to the armature current | |
| 36. |
In a D.C. series motor, if the armature current is reduced by 50%, the torque of the motor will be equal to |
| A. | 100% of the previous value |
| B. | 50% of the previous value |
| C. | 25% of the previous value |
| D. | 10% of the previous value |
| Answer» C. 25% of the previous value | |
| 37. |
The current drawn by the armature of D.C. motor is directly proportional to |
| A. | the torque required |
| B. | the speed of the motor |
| C. | the voltage across the terminals |
| D. | none of the above |
| Answer» A. the torque required | |
| 38. |
The power mentioned on the name plate of an electric motor indicates |
| A. | the power drawn in kW |
| B. | the power drawn in kVA |
| C. | the gross power |
| D. | the output power available at the shaft |
| Answer» D. the output power available at the shaft | |
| 39. |
Which D.C. motor has got maximum self loading property? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded 'motor |
| D. | Differentially compounded motor |
| Answer» D. Differentially compounded motor | |
| 40. |
Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavy loads? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» C. Cumulatively compounded motor | |
| 41. |
If a D.C. shunt motor is working at no load and if shunt field circuit suddenly opens |
| A. | nothing will happen to th£ 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» C. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses | |
| 42. |
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» D. in none of the above situations. | |
| 43. |
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» C. differentially compounded | |
| 44. |
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» C. in series with armature winding | |
| 45. |
Sparking at the commutator of a D.C. motor may result in |
| A. | damage to commutator segments |
| B. | damage to commutator insulation |
| C. | increased power consumption |
| D. | all of the above |
| Answer» D. all of the above | |
| 46. |
Which of the following motor is preferred for operation in highly explosive atmosphere ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» C. Air motor | |
| 47. |
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» C. Full-load current | |
| 48. |
Which one of the following is not the function of pole shoes in a D.C. machine ? |
| A. | To reduce eddy current loss |
| B. | To support the field coils |
| C. | To spread out flux for better unifor-mity |
| D. | To reduce the reluctance of the mag-netic path |
| Answer» A. To reduce eddy current loss | |
| 49. |
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is |
| A. | 4.0 |
| B. | 2.0 |
| C. | 1.0 |
| D. | 0.5 |
| Answer» D. 0.5 | |
| 50. |
For which of the following applications a D.C. motor is preferred over an A.C. motor ? |
| A. | Low speed operation |
| B. | High speed operation |
| C. | Variable speed operation |
| D. | Fixed speed operation |
| Answer» C. Variable speed operation | |
Done Studing? Take A Test.
Great job completing your study session! Now it's time to put your knowledge to the test. Challenge yourself, see how much you've learned, and identify areas for improvement. Don’t worry, this is all part of the journey to mastery. Ready for the next step? Take a quiz to solidify what you've just studied.