MCQOPTIONS
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MCQOPTIONS
This section includes 121 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.
| 1. |
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 | |
| 2. |
In D.C. generators the polarity of the interpoles_____________? |
| A. | is the same as that of the main pole ahead |
| B. | is the same as that of the immediately preceding pole |
| C. | is opposite to that of the main pole ahead |
| D. | is neutral as these poles do not play part in generating e.m.f. |
| Answer» B. is the same as that of the immediately preceding pole | |
| 3. |
A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave will_____________? |
| A. | will be zero |
| B. | will be of 5 Hz |
| C. | will be of 5 xiVHz |
| D. | will be of v Hz 5 |
| Answer» C. will be of 5 xiVHz | |
| 4. |
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 | |
| 5. |
Copper brushes in D.C. machine are used_____________? |
| A. | where low voltage and high currents are involved |
| B. | where high voltage and small cur-rents are involved |
| C. | in both of the above cases |
| D. | in none of the above cases |
| Answer» B. where high voltage and small cur-rents are involved | |
| 6. |
In case of D.C. machines, mechanical losses are primary function of____________? |
| A. | current |
| B. | voltage |
| C. | speed |
| D. | none of above |
| Answer» D. none of above | |
| 7. |
If a D.C. generator fails to build up the probable cause could not be_____________? |
| A. | imperfect brush contact |
| B. | field resistance less than the critical resistance |
| C. | no residual magnetism in the generator |
| D. | faulty shunt connections tending to reduce the residual magnetism |
| Answer» C. no residual magnetism in the generator | |
| 8. |
In a four-pole D.C. machine____________? |
| A. | all the four poles are north poles |
| B. | alternate poles are north and south |
| C. | all the four poles are south poles |
| D. | two north poles follow two south poles |
| Answer» C. all the four poles are south poles | |
| 9. |
A separately excited generator as compared to a self-excited generator_____________? |
| A. | is amenable to better voltage control |
| B. | is more stable |
| C. | has exciting current independent of load current |
| D. | has all above features |
| Answer» E. | |
| 10. |
In lap winding, the number of brushes is always_____________? |
| A. | double the number of poles |
| B. | same as the number of poles |
| C. | half the number of poles |
| D. | two |
| Answer» C. half the number of poles | |
| 11. |
In D.C. generators, the cause of rapid brush wear may be___________? |
| A. | severe sparking |
| B. | rough commutator surface |
| C. | imperfect contact |
| D. | any of the above |
| Answer» E. | |
| 12. |
The bearings used to support the rotor shafts are generally______________? |
| A. | ball bearings |
| B. | bush bearings |
| C. | magnetic bearmgs |
| D. | needle bearings |
| Answer» B. bush bearings | |
| 13. |
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 | |
| 14. |
In D.C. generators the pole shoes are fastened to the pole core by_____________? |
| A. | rivets |
| B. | counter sunk screws |
| C. | brazing |
| D. | welding |
| Answer» C. brazing | |
| 15. |
Fleming’s right-hand rule regarding direction of induced e.m.f., correlates__________? |
| A. | magnetic flux, direction of current flow and resultant force |
| B. | magnetic flux, direction of motion and the direction of e.m.f. induced |
| C. | magnetic field strength, induced voltage and current |
| D. | magnetic flux, direction of force and direction of motion of conductor |
| Answer» C. magnetic field strength, induced voltage and current | |
| 16. |
Eddy currents are induced in the pole shoes of a D.C. machine due to______________? |
| A. | oscillating magnetic field |
| B. | pulsating magnetic flux |
| C. | relative rotation between field and armature |
| D. | all above |
| Answer» D. all above | |
| 17. |
Armature reaction of an unsaturated D.C. machine is_____________? |
| A. | crossmagnetising |
| B. | demagnetising |
| C. | magnetising |
| D. | none of above |
| Answer» B. demagnetising | |
| 18. |
Equilizer rings are required in case armature is_______________? |
| A. | wave wound |
| B. | lap wound |
| C. | delta wound |
| D. | duplex wound |
| Answer» C. delta wound | |
| 19. |
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. | |
| 20. |
Welding generator will have____________? |
| A. | lap winding |
| B. | wave winding |
| C. | delta winding |
| D. | duplex wave winding |
| Answer» B. wave winding | |
| 21. |
For a D.C. machines laboratory following type of D.C. supply will be suitable___________? |
| A. | rotary converter |
| B. | mercury are rectifier |
| C. | induction motor D.C. generator set |
| D. | synchronous motor D.C. generator set |
| Answer» D. synchronous motor D.C. generator set | |
| 22. |
Flashing the field of D.C. generator means:______________? |
| A. | neutralising residual magnetism |
| B. | creating residual magnetism by a D.C. source |
| C. | making the magnetic losses of forces parallel |
| D. | increasing flux density by adding extra turns of windings on poles |
| Answer» C. making the magnetic losses of forces parallel | |
| 23. |
In case of D.C. machine winding, number of commutator segments is equal to______________? |
| A. | number of armature coils |
| B. | number of armature coil sides |
| C. | number of armature conductors |
| D. | number of armature turns |
| Answer» B. number of armature coil sides | |
| 24. |
Iron losses in a D.C. machine are independent of variations in______________? |
| A. | speed |
| B. | load |
| C. | voltage |
| D. | speed and voltage |
| Answer» C. voltage | |
| 25. |
The function of pole shoes in the case of D.C. machine is______________? |
| A. | to reduce the reluctance of the mag¬netic path |
| B. | to spread out the flux to achieve uniform flux density |
| C. | to support the field coil |
| D. | to discharge all the above functions |
| Answer» E. | |
| 26. |
In D.C. generators, current to the external circuit from armature is given through_____________? |
| A. | commutator |
| B. | solid connection |
| C. | slip rings |
| D. | none of above |
| Answer» B. solid connection | |
| 27. |
Brushes of D.C. machines are made of_________? |
| A. | carbon |
| B. | soft copper |
| C. | hard copper |
| D. | all of above |
| Answer» B. soft copper | |
| 28. |
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. | |
| 29. |
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 | |
| 30. |
The armature of D.C. generator is laminated to_______________? |
| A. | reduce the bulk |
| B. | provide the bulk |
| C. | insulate the core |
| D. | reduce eddy current loss |
| Answer» E. | |
| 31. |
Laminations of core are generally made of________________? |
| A. | case iron |
| B. | carbon |
| C. | silicon steel |
| D. | stainless steel |
| Answer» D. stainless steel | |
| 32. |
In a commutator_____________? |
| A. | copper is harder than mica |
| B. | mica and copper are equally hard |
| C. | mica is harder than copper |
| D. | none of the above |
| Answer» D. none of the above | |
| 33. |
According to Fleming’s right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of____________? |
| A. | motion of conductor |
| B. | lines of force |
| C. | either of the above |
| D. | none of the above |
| Answer» C. either of the above | |
| 34. |
The resistance of armature winding depends on |
| A. | length of conductor |
| B. | cross-sectional area of the conductor |
| C. | number of conductors |
| D. | all of the above |
| Answer» E. | |
| 35. |
The field coils of D.C. generator are usually made of_____________? |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» C. cast iron | |
| 36. |
The commutator segments are connected to the armature conductors by means of___________? |
| A. | copper lugs |
| B. | resistance wires |
| C. | insulation pads |
| D. | brazing |
| Answer» B. resistance wires | |
| 37. |
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 | |
| 38. |
Iron losses in a D.C. machine are independent of variations in_____________? |
| A. | speed |
| B. | load |
| C. | voltage |
| D. | speed and voltage |
| Answer» C. voltage | |
| 39. |
The material for commutator brushes is generally_______________? |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» E. | |
| 40. |
The insulating material used between the commutator segments is normally_____________? |
| A. | graphite |
| B. | paper |
| C. | mica |
| D. | insulating varnish |
| Answer» D. insulating varnish | |
| 41. |
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 | |
| 42. |
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 mag¬netisation |
| C. | crossmagnetisation as well as demagnetising |
| D. | cross magnetisation only |
| Answer» D. cross magnetisation only | |
| 43. |
In the case of lap winding resultant pitch is____________? |
| A. | multiplication of front and back pitches |
| B. | division of front pitch by back pitch |
| C. | sum of front and back pitches |
| D. | difference of front and back pitches |
| Answer» E. | |
| 44. |
In a D.C. generator:___________________? |
| A. | external resistance = internal char-acteristic – armature reaction |
| B. | internal characteristic = magnetisation characteristic – ohmic drop |
| C. | external characteristic = magnetisation characteristic – ohmic drop – armature reaction |
| D. | magnetisation characteristic = external characteristic |
| Answer» D. magnetisation characteristic = external characteristic | |
| 45. |
Which of the following generating machine will offer constant voltage on all loads? |
| A. | Self-excited generator |
| B. | Separately excited generator |
| C. | Level compounded generator |
| D. | All of the above |
| Answer» D. All of the above | |
| 46. |
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 | |
| 47. |
Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be_____________________? |
| A. | 270 V |
| B. | 267.5 V |
| C. | 265 V |
| D. | 257.4 V |
| Answer» C. 265 V | |
| 48. |
The essential condition for parallel operation of two D.C. generators is that they have ________________? |
| A. | same kW rating |
| B. | the same operation r.p.m. |
| C. | the same drooping voltage characteristics |
| D. | same percentage regulation |
| Answer» D. same percentage regulation | |
| 49. |
When two D.C. generators are running in parallel an equilizer bar is used______________? |
| A. | to increase the series flux |
| B. | to increase the generated e.m.f. |
| C. | to reduce the combined effect of ar-mature reaction of both the machines |
| D. | so that the two identical machines will pass approximately equal cur¬rents to the load |
| Answer» E. | |
| 50. |
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. | |