MCQOPTIONS
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MCQOPTIONS
This section includes 49 Mcqs, each offering curated multiple-choice questions to sharpen your C-DAC knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
D.C. series generator is used |
| A. | to supply traction load |
| B. | to supply industrial load at constant voltage |
| C. | voltage at the toad end of the feeder |
| D. | for none of the above purpose |
| Answer» D. for none of the above purpose | |
| 2. |
Open circuited armature coil of a D.C. machine is |
| A. | identified by the scarring of the commutator segment to which open circuited coil is connected |
| B. | indicated by a spark completely around the commutator |
| C. | both (a) and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 3. |
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» E. | |
| 4. |
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» B. copper | |
| 5. |
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» D. None of the above | |
| 6. |
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» C. 3 : 2 | |
| 7. |
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» D. using equiliser rings | |
| 8. |
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 | |
| 9. |
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» D. none of the above | |
| 10. |
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» E. | |
| 11. |
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» B. permanent magnets | |
| 12. |
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» B. increases armature speed | |
| 13. |
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» E. | |
| 14. |
A D.C. welding generator has |
| A. | lap winding |
| B. | wave moving |
| C. | duplex winding |
| D. | any of the above |
| Answer» B. wave moving | |
| 15. |
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. | |
| 16. |
synchronous motor D.C. generator set |
| 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» E. | |
| 17. |
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 | |
| 18. |
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 | |
| 19. |
Welding generator will have |
| A. | lap winding |
| B. | wave winding |
| C. | delta winding |
| D. | duplex wave winding |
| Answer» B. wave winding | |
| 20. |
Equilizer rings are required in case armature is |
| A. | wave wound |
| B. | lap wound |
| C. | delta wound |
| D. | duplex wound |
| Answer» C. delta wound | |
| 21. |
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 | |
| 22. |
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. | |
| 23. |
Armature reaction of an unsaturated D.C. machine is |
| A. | crossmagnetising |
| B. | demagnetising |
| C. | magnetising |
| D. | none of above |
| Answer» B. demagnetising | |
| 24. |
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 | |
| 25. |
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 | |
| 26. |
The insulating material used between the commutator segments is normally |
| A. | graphite |
| B. | paper |
| C. | mica |
| D. | insulating varnish |
| Answer» D. insulating varnish | |
| 27. |
The material for commutator brushes is generally |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» E. | |
| 28. |
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 | |
| 29. |
Brushes of D.C. machines are made of |
| A. | carbon |
| B. | soft copper |
| C. | hard copper |
| D. | all of above |
| Answer» B. soft copper | |
| 30. |
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 | |
| 31. |
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 | |
| 32. |
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 | |
| 33. |
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» E. | |
| 34. |
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 | |
| 35. |
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 | |
| 36. |
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 | |
| 37. |
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. | |
| 38. |
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 | |
| 39. |
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. | |
| 40. |
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 conductormagnetic flux, direction of force and direction of motion of conductor |
| Answer» C. magnetic field strength, induced voltage and current | |
| 41. |
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 | |
| 42. |
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 | |
| 43. |
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 | |
| 44. |
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 | |
| 45. |
The field coils of D.C. generator are usually made of |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» C. cast iron | |
| 46. |
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. | |
| 47. |
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. | |
| 48. |
Which of the following could be lamina-proximately the thickness of lamina-tions of a D.C. machine ? |
| A. | 0.005 mm |
| B. | 0.05 mm |
| C. | 0.5 m |
| D. | 5 m |
| Answer» D. 5 m | |
| 49. |
Laminations of core are generally made of |
| A. | case iron |
| B. | carbon |
| C. | silicon steel |
| D. | stainless steel |
| Answer» D. stainless steel | |