MCQOPTIONS
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MCQOPTIONS
This section includes 33 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which of the following could be lamina-proximately the thickness of laminations of a D.C. machine ? |
| A. | 0.005 mm |
| B. | 0.05 mm |
| C. | 0.5 m |
| D. | 5 m |
| Answer» D. 5 m | |
| 2. |
While applying Fleming's right-hand rule to And the direction of induced e.m.f., the thumb points towards |
| A. | direction of induced e.m.f. |
| B. | direction of flux |
| C. | direction of motion of the conductor if forefinger points in the direction of generated e.m.f. |
| D. | direction of motion of conductor, if forefinger points along the lines of flux |
| Answer» E. | |
| 3. |
For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ? |
| A. | Lap winding |
| B. | Wave winding |
| C. | Either of (a) and (b) above |
| D. | Depends on other features of design |
| Answer» C. Either of (a) and (b) above | |
| 4. |
In D.C. generators, the brushes on commutator remain in contact with conductors which |
| A. | lie under south pole |
| B. | lie under north pole |
| C. | lie under interpolar region |
| D. | are farthest from the poles |
| Answer» D. are farthest from the poles | |
| 5. |
If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be |
| A. | demagnetisation only |
| B. | cross magnetisation as well as magnetisation |
| C. | crossmagnetisation as well as demagnetising |
| D. | cross magnetisation only |
| Answer» D. cross magnetisation only | |
| 6. |
If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be |
| A. | 5 kV/mm |
| B. | 10 kV/mm |
| C. | 15 kV/mm |
| D. | 30 kV/mm |
| Answer» C. 15 kV/mm | |
| 7. |
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be |
| A. | 150 V |
| B. | less than 150 V |
| C. | greater than 150 V |
| D. | none of the above |
| Answer» D. none of the above | |
| 8. |
The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage |
| A. | will be less than 250 V |
| B. | will always be 250 V |
| C. | may be greater or less than 250 V |
| D. | none of the above |
| Answer» D. none of the above | |
| 9. |
The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is |
| A. | 2 |
| B. | 4 |
| C. | 6 |
| D. | 8 |
| Answer» C. 6 | |
| 10. |
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 | |
| 11. |
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. | |
| 12. |
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 resis tance |
| Answer» B. increase the field resistance | |
| 13. |
If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be |
| A. | 2 cm |
| B. | 10 cm |
| C. | 50 cm |
| D. | 400 cm |
| Answer» D. 400 cm | |
| 14. |
In congested areas where excavation is expensive and inconvenient 'draw in system' of laying of underground cables is often adopted. |
| A. | Yes |
| B. | No |
| C. | none |
| D. | none |
| Answer» B. No | |
| 15. |
In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called |
| A. | rotor |
| B. | stator |
| C. | field |
| D. | armature |
| Answer» E. | |
| 16. |
In a D.C. generator in case the resistance of the field winding is increased, then output voltage will |
| A. | increase |
| B. | decrease |
| C. | remain unaffected |
| D. | fluctuate heavily |
| Answer» C. remain unaffected | |
| 17. |
Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Compound generator |
| D. | None of the above |
| Answer» E. | |
| 18. |
Which of the following generator will have negligible terminal voltage while running on no-load ? |
| A. | Series generator |
| B. | Shunt generator |
| C. | Compound generator |
| D. | Separately excited generator |
| Answer» B. Shunt generator | |
| 19. |
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. | |
| 20. |
A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave |
| A. | will be zero |
| B. | will be of 5 Hz |
| C. | willbeof5xiVHz |
| D. | will be of v Hz 5 |
| Answer» C. willbeof5xiVHz | |
| 21. |
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 | |
| 22. |
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 | |
| 23. |
Which of the following generators will be preferred if they are required to be run in parallel ? |
| A. | Shunt generators |
| B. | Series generators |
| C. | Compound generators |
| D. | None of the above |
| Answer» B. Series generators | |
| 24. |
Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ? |
| A. | The direction of that generator is reversed |
| B. | The speed of that generator is increased |
| C. | The field of that generator is weakened |
| D. | That generator takes large share of loads |
| Answer» E. | |
| 25. |
D.C. generators are connected to the busbars or disconnected from them only under the floating condition |
| A. | to avoid sudden loading of the primemover |
| B. | to avoid mechanicaljerk to the shaft |
| C. | to avoid burning of switch contacts |
| D. | all above |
| Answer» E. | |
| 26. |
In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when |
| A. | r.p.m. is more than 300 |
| B. | r.p.m. is less than 300 |
| C. | number of poles is 4 |
| D. | number of poles is 2 |
| Answer» E. | |
| 27. |
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 | |
| 28. |
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 | |
| 29. |
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 |
| Answer» B. in magnetic neutral axis | |
| 30. |
Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ? |
| A. | Dummy coils |
| B. | Commutator |
| C. | Eye bolt |
| D. | Equilizer rings |
| Answer» C. Eye bolt | |
| 31. |
If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by |
| A. | Blv |
| B. | Blv2 |
| C. | Bl2v |
| D. | Bl2v2 |
| Answer» B. Blv2 | |
| 32. |
In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be |
| A. | 4 |
| B. | 8 |
| C. | 16 |
| D. | 32 |
| Answer» C. 16 | |
| 33. |
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 | |