McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .
| 1. |
Laminations of core are generally made of |
| A. | case iron |
| B. | carbon |
| C. | silicon steel |
| D. | stainless steel |
| Answer» C. silicon steel | |
| 2. |
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» C. 0.5 m | |
| 3. |
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» D. reduce eddy current loss | |
| 4. |
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» D. all of the above | |
| 5. |
The field coils of D.C. generator are usually made of |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» B. copper | |
| 6. |
The commutator segments are connected to the armature conductors by means of |
| A. | copper lugs |
| B. | resistance wires |
| C. | insulation pads |
| D. | brazing |
| Answer» A. copper lugs | |
| 7. |
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» C. mica is harder than copper | |
| 8. |
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» B. counter sunk screws | |
| 9. |
Satisfactory commutation of D.C. machines requires |
| A. | brushes should be of proper grade and size |
| B. | brushes should smoothly run in the holders |
| C. | smooth, concentric commutator properly undercut |
| D. | all of the above |
| Answer» D. all of the above | |
| 10. |
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» B. magnetic flux, direction of motion and the direction of e.m.f. induced | |
| 11. |
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» D. direction of motion of conductor, if forefinger points along the lines of flux | |
| 12. |
The bearings used to support the rotor shafts are generally |
| A. | ball bearings |
| B. | bush bearings |
| C. | magnetic bearmgs |
| D. | needle bearings |
| Answer» A. ball bearings | |
| 13. |
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» D. any of the above | |
| 14. |
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» B. same as the number of poles | |
| 15. |
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» B. Wave winding | |
| 16. |
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» B. alternate poles are north and south | |
| 17. |
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» A. where low voltage and high currents are involved | |
| 18. |
A separately excited generator as compared to a self-excited generator |
| A. | is amenable to better voltage con-trol |
| B. | is more stable |
| C. | has exciting current independent of load current |
| D. | has all above features |
| Answer» D. has all above features | |
| 19. |
In case of D.C. machines, mechanical losses are primary function of |
| A. | current |
| B. | voltage |
| C. | speed |
| D. | none of above |
| Answer» C. speed | |
| 20. |
Iron losses in a D.C. machine are independent of variations in |
| A. | speed |
| B. | load |
| C. | voltage |
| D. | speed and voltage |
| Answer» B. load | |
| 21. |
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» A. commutator | |
| 22. |
Brushes of D.C. machines are made of |
| A. | carbon |
| B. | soft copper |
| C. | hard copper |
| D. | all of above |
| Answer» A. carbon | |
| 23. |
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» A. Blv | |
| 24. |
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» B. 8 | |
| 25. |
The material for commutator brushes is generally |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» D. carbon | |
| 26. |
The insulating material used between the commutator segments is normally |
| A. | graphite |
| B. | paper |
| C. | mica |
| D. | insulating varnish |
| Answer» C. mica | |
| 27. |
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» C. lie under interpolar region | |
| 28. |
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» C. crossmagnetisation as well as demagnetising | |
| 29. |
Armature reaction of an unsaturated D.C. machine is |
| A. | crossmagnetising |
| B. | demagnetising |
| C. | magnetising |
| D. | none of above |
| Answer» A. crossmagnetising | |
| 30. |
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» D. all above | |
| 31. |
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» C. relative rotation between field and armature | |
| 32. |
Equilizer rings are required in case armature is |
| A. | wave wound |
| B. | lap wound |
| C. | delta wound |
| D. | duplex wound |
| Answer» B. lap wound | |
| 33. |
Welding generator will have |
| A. | lap winding |
| B. | wave winding |
| C. | delta winding |
| D. | duplex wave winding |
| Answer» A. lap winding | |
| 34. |
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» A. number of armature coils | |
| 35. |
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» C. induction motor D.C. generator set | |
| 36. |
The function of pole shoes in the case of D.C. machine is |
| A. | to reduce the reluctance of the magnetic 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» D. to discharge all the above functions | |
| 37. |
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» D. difference of front and back pitches | |
| 38. |
A D.C. welding generator has |
| A. | lap winding |
| B. | wave moving |
| C. | duplex winding |
| D. | any of the above |
| Answer» A. lap winding | |
| 39. |
Which of the following statement about D.C. generators is false ? |
| A. | Compensating winding in a D.C. machine helps in commutation |
| B. | In a D. C. generator interpoles winding is connected in series with the armature winding |
| C. | Back pitch and front pitch are both odd and approximately equal to the pole pitch |
| D. | Equilizing bus bars are used with parallel running of D.C. shunt generators |
| Answer» D. Equilizing bus bars are used with parallel running of D.C. shunt generators | |
| 40. |
The demagnetising component of armature reaction in a D.C. generator |
| A. | reduces generator e.m.f. |
| B. | increases armature speed |
| C. | reduces interpoles flux density |
| D. | results in sparking trouble |
| Answer» A. reduces generator e.m.f. | |
| 41. |
Magnetic field in a D.C. generator is produced by |
| A. | electromagnets |
| B. | permanent magnets |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» A. electromagnets | |
| 42. |
The number of brushes in a commutator depends on |
| A. | speed of armature |
| B. | type of winding |
| C. | voltage |
| D. | amount of current to be collected |
| Answer» D. amount of current to be collected | |
| 43. |
Compensating windings are used in D.C. generators |
| A. | mainly to reduce the eddy currents by providing local short-circuits |
| B. | to provide path for the circulation of cooling air |
| C. | to neutralise the cross-magnetising effect of the armature reaction |
| D. | none of the above |
| Answer» C. to neutralise the cross-magnetising effect of the armature reaction | |
| 44. |
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» B. Commutator | |
| 45. |
In a D.C. generator the ripples in the direct e.m.f. generated are reduced by |
| A. | using conductor of annealed copper |
| B. | using commutator with large number of segments |
| C. | using carbon brushes of superior quality |
| D. | using equiliser rings |
| Answer» C. using carbon brushes of superior quality | |
| 46. |
In D.C. generators, lap winding is used for |
| A. | high voltage, high current |
| B. | low voltage, high current |
| C. | high voltage, low current |
| D. | low voltage, low current |
| Answer» B. low voltage, high current | |
| 47. |
Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be |
| A. | 2 : 3 |
| B. | 3 : 1 |
| C. | 3 : 2 |
| D. | 1 : 3 |
| Answer» B. 3 : 1 | |
| 48. |
The voltage drop for which of the following types of brush can be expected to be least ? |
| A. | Graphite brushes |
| B. | Carbon brushes |
| C. | Metal graphite brushes |
| D. | None of the above |
| Answer» C. Metal graphite brushes | |
| 49. |
The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be |
| A. | E/2 |
| B. | 2E |
| C. | slightly less than E |
| D. | E |
| Answer» B. 2E | |
| 50. |
The armature core of a D.C. generator is usually made of |
| A. | silicon steel |
| B. | copper |
| C. | non-ferrous material |
| D. | cast-iron |
| Answer» A. silicon steel | |
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.