MCQOPTIONS
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MCQOPTIONS
This section includes 252 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Calculate the time period of the waveform v(t)=12sin(8πt+8π÷15)+144sin(2πt+π÷6)+ 445sin(πt+7π÷6). |
| A. | 8 sec |
| B. | 4 sec |
| C. | 7 sec |
| D. | 3 sec |
| Answer» C. 7 sec | |
| 2. |
If induction motor air gap power is 1.8 KW and gross developed power is .1 KW, then rotor ohmic loss will be KW. |
| A. | 1.7 |
| B. | 2.7 |
| C. | 3.7 |
| D. | 4.7 |
| Answer» B. 2.7 | |
| 3. |
A 2-pole, 3-phase, Hz induction motor is operating at a speed of 550 rpm. The frequency of the rotor current of the motor in Hz is 2. |
| A. | 9.98 |
| B. | 9.71 |
| C. | 9.12 |
| D. | 9.37 |
| Answer» E. | |
| 4. |
Calculate the moment of inertia of the disc having a mass of 54 kg and diameter of 91 cm. |
| A. | 5.512 kgm2 |
| B. | 5.589 kgm2 |
| C. | 5.487 kgm2 |
| D. | 5.018 kgm2 |
| Answer» C. 5.487 kgm2 | |
| 5. |
DC machines have windings and synchronous machines use windings. |
| A. | closed,open |
| B. | open, closed |
| C. | open, open |
| D. | closed, closed |
| Answer» B. open, closed | |
| 6. |
A starter is required for a 220-V shunt motor. The maximum allowable current is 55 A and the minimum current is about 35 A. The armature resistance of the motor is 0.4 Ω. What will be the number of sections of starter resistance required? |
| A. | 5 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» D. 8 | |
| 7. |
The flux and the internally generated voltage of a dc machine is a function of its magneto-motive force. |
| A. | non-linear |
| B. | linear |
| C. | constant |
| D. | inverse |
| Answer» B. linear | |
| 8. |
Second lowest order harmonic present in 3-Φ fully controlled rectifier is |
| A. | 5th |
| B. | 7th |
| C. | 3rd |
| D. | 2nd |
| Answer» C. 3rd | |
| 9. |
applications. |
| A. | power generation |
| B. | electric heating |
| C. | conveyor belt motion |
| D. | power transmission |
| Answer» C. conveyor belt motion | |
| 10. |
motor. The maximum allowable current is 55 A and the minimum current is about 35 A. The armature resistance of the motor is 0.4 Ω. What will be the number of sections of starter resistance required? |
| A. | 5 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» D. 8 | |
| 11. |
The slope of the V-I curve is 5°. Calculate the value of resistance. Assume the relationship between voltage and current is a straight line. |
| A. | .3254 Ω |
| B. | .3608 Ω |
| C. | .3543 Ω |
| D. | .3443 Ω |
| Answer» E. | |
| 12. |
Calculate the total heat dissipated in a resistor of 44 Ω when 0 A current flows through it. |
| A. | 0 w |
| B. | 2 w |
| C. | 1.5 w |
| D. | .3 w |
| Answer» B. 2 w | |
| 13. |
Calculate the heat loss in the electric motor for time interval 0-5 sec using the following data: Ia=2 A, Ra=.8Ω. |
| A. | 16 j-sec |
| B. | 14 j-sec |
| C. | 12 j-sec |
| D. | 10 j-sec |
| Answer» B. 14 j-sec | |
| 14. |
Calculate the active power in a 788 ω resistor with 178 A current flowing through it. |
| A. | 24.96 mw |
| B. | 24.44 mw |
| C. | 24.12 mw |
| D. | 26.18 mw |
| Answer» B. 24.44 mw | |
| 15. |
Calculate the average value of the sinusoidal waveform x(t)=848sin(1.65πt+2π÷0.68). |
| A. | 0 |
| B. | 78 v |
| C. | 15 v |
| D. | 85 v |
| Answer» B. 78 v | |
| 16. |
Calculate the phase angle of the sinusoidal waveform z(t)=78sin(456πt+2π÷78). |
| A. | π÷39 |
| B. | 2π÷5 |
| C. | π÷74 |
| D. | 2π÷4 |
| Answer» B. 2π÷5 | |
| 17. |
If the students give a forward shift of 10° to the dc generator, then it |
| A. | reduces flux per pole |
| B. | improves flux per pole |
| C. | increases the flux density in core |
| D. | none of the mentioned |
| Answer» B. improves flux per pole | |
| 18. |
voltage of a dc machine is a function of its magneto-motive force. |
| A. | non-linear |
| B. | linear |
| C. | constant |
| D. | inverse |
| Answer» B. linear | |
| 19. |
-Φ fully controlled rectifier is |
| A. | 5th |
| B. | 7th |
| C. | 3rd |
| D. | 2nd |
| Answer» C. 3rd | |
| 20. |
Calculate the compensator rating required for a sec(Φ)=1. |
| A. | 0.64 p.u |
| B. | 0.21 p.u |
| C. | 0.57 p.u |
| D. | 0 p.u |
| Answer» E. | |
| 21. |
γ is given as 1.585. Resistance at maximum allowable current is given equal to 4 Ω, what is the 5th step resistance? |
| A. | 0.235 |
| B. | 0.370 |
| C. | 1.476 |
| D. | 2 |
| Answer» B. 0.370 | |
| 22. |
Plugging is applied in a motor, if we don’t make the switch OFF what will happen? |
| A. | motor will come to rest as a result of plugging |
| B. | motor will come to rest and will start rotating in another direction |
| C. | motor will burn |
| D. | nothing will happen |
| Answer» C. motor will burn | |
| 23. |
devices were used for voltage control applications. |
| A. | cycloconverters |
| B. | vacuum tubes |
| C. | tap changing transformer |
| D. | induction machine |
| Answer» D. induction machine | |
| 24. |
(II) If a large 3–phase squirrel-cage induction motor with no load is started at full voltage, it will be damaged. |
| A. | i is true, ii is false |
| B. | i is true and ii is also true |
| C. | i is false, ii is true |
| D. | i and ii are false |
| Answer» B. i is true and ii is also true | |
| 25. |
In the below given voltage controller circuit |
| A. | the positive half cycle at the load is same as the supply vs |
| B. | the negative half cycle at the load is same as the supply vs |
| C. | the positive and negative half cycles at the load are identical to the supply |
| D. | none of the mentioned |
| Answer» C. the positive and negative half cycles at the load are identical to the supply | |
| 26. |
A single-phase half wave voltage controller consists of |
| A. | one scr is parallel with one diode |
| B. | one scr is anti parallel with one diode |
| C. | two scrs in parallel |
| D. | two scrs in anti parallel |
| Answer» C. two scrs in parallel | |
| 27. |
The slip recovery scheme is a part of the synchronous speed changing technique. |
| A. | true |
| B. | false |
| Answer» B. false | |
| 28. |
In the rotor voltage injection method, when an external voltage source is in opposite phase with the main voltage then speed will |
| A. | increase |
| B. | decrease |
| C. | remain unchanged |
| D. | first increases then decrease |
| Answer» C. remain unchanged | |
| 29. |
A 2-pole, 3-phase, Â Â Â Â Â Â Â Â Â Â Â Â Â Hz induction motor is operating at a speed of 550 rpm. The frequency of the rotor current of the motor in Hz is 2. |
| A. | 9.98 |
| B. | 9.71 |
| C. | 9.12 |
| D. | 9.37 |
| Answer» E. | |
| 30. |
In the rotor voltage injection method, when an external voltage source is in phase with the main voltage then speed will |
| A. | increase |
| B. | decrease |
| C. | remain unchanged |
| D. | first increases then decrease |
| Answer» B. decrease | |
| 31. |
1 SPEED CONTROL OF THREE PHASE INDUCTION MOTOR |
| A. | slip frequency |
| B. | supply frequency |
| C. | the frequency corresponding to rotor speed |
| D. | zero |
| Answer» B. supply frequency | |
| 32. |
The disadvantage of the Ward Leonard control method is |
| A. | high initial cost |
| B. | high maintenance cost |
| C. | low efficiency at high loads |
| D. | high cost, high maintenance and low efficiency |
| Answer» E. | |
| 33. |
Speed control by Ward Leonard method, can give uniform speed variation |
| A. | in both directions |
| B. | in one direction |
| C. | below normal speed only |
| D. | above normal speed only. |
| Answer» B. in one direction | |
| 34. |
1 = 0.0917. |
| A. | reduce armature voltage |
| B. | increase armature voltage |
| C. | increase field current |
| D. | decrease field current |
| Answer» B. increase armature voltage | |
| 35. |
A 6-pole lap wound DC generator has a developed power of P watts and brush voltage of E volts. Three adjacent brushes of the machine had been found worn out and got open circuited. If the machine is operated with the remaining brushes, voltage and power that could be obtained from the machine are |
| A. | e, p |
| B. | e, 2p/3 |
| C. | e/p, 2p/3 |
| D. | e, p/3 |
| Answer» B. e, 2p/3 | |
| 36. |
The commutator pitch for a simplex lap winding is equal to |
| A. | 1 and -1 |
| B. | 1 |
| C. | -1 |
| D. | 2 to -2 |
| Answer» B. 1 | |
| 37. |
DC machines have                  windings and synchronous machines use              windings. |
| A. | closed,open |
| B. | open, closed |
| C. | open, open |
| D. | closed, closed |
| Answer» B. open, closed | |
| 38. |
Why does DC motor sometimes run too fast when under-loaded? |
| A. | due to weak field |
| B. | due to high line voltage |
| C. | due to brush-shifted to neutral |
| D. | all of the mentioned |
| Answer» B. due to high line voltage | |
| 39. |
Run-away for large DC machine is avoided by using |
| A. | a turn or two of cumulative compounding |
| B. | compensating winding |
| C. | stablizer winding |
| D. | all of the mentioned |
| Answer» C. stablizer winding | |
| 40. |
To implement armature voltage control, it must be ensured that |
| A. | it is used on separately excited machine |
| B. | it is used on shunt machine |
| C. | it is used on series machine |
| D. | any of the mentioned machine |
| Answer» B. it is used on shunt machine | |
| 41. |
Small DC motors have best speed control by |
| A. | armature voltage control |
| B. | field resistance control |
| C. | any of the methods |
| D. | none of the mentioned |
| Answer» B. field resistance control | |
| 42. |
At a very low speed, increase in field resistance will |
| A. | decrease the speed of motor |
| B. | increase the speed of motor |
| C. | not have signicant effect on speed |
| D. | no effect |
| Answer» B. increase the speed of motor | |
| 43. |
The post effects of the armature reaction is |
| A. | main field distortion |
| B. | shift in mna |
| C. | reduction in main field |
| D. | none of the mentioned |
| Answer» E. | |
| 44. |
For a 7.46 kW, 200 V dc shunt motor with full load efficiency of 85% has armature resistance of 0.25 ohms. Calculate the value of starting resistance in ohms for a current 1.5 times of the full load current. |
| A. | 2.788 |
| B. | 3.038 |
| C. | 2.688 |
| D. | 2.588 |
| Answer» B. 3.038 | |
| 45. |
Thyristor controlled starter is preferred over DOL starter due to |
| A. | lesser losses |
| B. | controlled direction |
| C. | least resistance offered |
| D. | all of the mentioned |
| Answer» B. controlled direction | |
| 46. |
The shunt motor starters that can be used is/are |
| A. | 3-point and 4-point starter |
| B. | 5-point starter |
| C. | 4-point starter |
| D. | 5-point and 3-point starter |
| Answer» B. 5-point starter | |
| 47. |
2 TYPICAL CONTROL CIRCUITS FOR SHUNT AND SERIES MOTORS |
| A. | starting resistance would burn |
| B. | field winding would burn |
| C. | speed will rise steeply |
| D. | any of the mentioned |
| Answer» B. field winding would burn | |
| 48. |
A starting resistance is inserted at the starting in an induction motor as well as dc motor. |
| A. | induction motor has to control starting torque whereas in dc motor, it is done to avoid large current |
| B. | to limit starting current in both the machines |
| C. | to limit starting speed |
| D. | all of the mentioned |
| Answer» B. to limit starting current in both the machines | |
| 49. |
A starter is required for a 220-V shunt motor. The maximum allowable current is 55 A and the minimum current is about 35 A. The armature resistance of the motor is 0.4 Ω. What will be the number of sections of starter resistance required? |
| A. | 5 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» D. 8 | |
| 50. |
What will happen if DC motor is used without starter? |
| A. | heavy sparking at brushes |
| B. | it’ll start smoothly |
| C. | will not start at all |
| D. | depends on load |
| Answer» B. it’ll start smoothly | |