MCQOPTIONS
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MCQOPTIONS
This section includes 109 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. |
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. | |
| 2. |
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. | |
| 3. |
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 | |
| 4. |
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 | |
| 5. |
When two D.C. series generators are running in parallel, an equilizer bar is used________________? |
| A. | to increase the speed and hence generated e.m.f. |
| B. | to increase the series flux |
| C. | so that two similar machines will pass approximately equal currents to the load |
| D. | to reduce the combined effect of ar-mature reaction of both machines |
| Answer» D. to reduce the combined effect of ar-mature reaction of both machines | |
| 6. |
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. | |
| 7. |
Welding generator will have____________? |
| A. | lap winding |
| B. | wave winding |
| C. | delta winding |
| D. | duplex wave winding |
| Answer» B. wave winding | |
| 8. |
Wave winding is composed of_______________? |
| A. | any even number of conductors |
| B. | any odd number of conductors |
| C. | that even number which is exact multiple of poles + 2 |
| D. | that even number which is exact multiple of poles |
| Answer» D. that even number which is exact multiple of poles | |
| 9. |
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. | |
| 10. |
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 | |
| 11. |
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 | |
| 12. |
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 |
| D. | none |
| Answer» B. in magnetic neutral axis | |
| 13. |
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. | |
| 14. |
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 | |
| 15. |
The series field of a short-shunt D.C. generator is excited by_______________? |
| A. | external current |
| B. | armature current |
| C. | shunt current |
| D. | load current |
| Answer» E. | |
| 16. |
The rapid wear of brushes takes place due to____________? |
| A. | abrasion from dust |
| B. | excessive spring pressure |
| C. | rough commutator bars |
| D. | high mica insulation between com-mutation bars |
| E. | all of the above factors |
| Answer» F. | |
| 17. |
The purpose of providing dummy coils in a generator is__________________? |
| A. | to reduce eddy current losses |
| B. | to enhance flux density |
| C. | to amplify voltage |
| D. | to provide mechanical balance for the rotor |
| Answer» E. | |
| 18. |
The purpose of providing dummy coils in a generator is____________? |
| A. | to reduce eddy current losses |
| B. | to enhance flux density |
| C. | to amplify voltage |
| D. | to provide mechanical balance for the rotor |
| Answer» E. | |
| 19. |
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 | |
| 20. |
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. | |
| 21. |
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 | |
| 22. |
The material for commutator brushes is generally_______________? |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» E. | |
| 23. |
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 | |
| 24. |
The insulating material used between the commutator segments is normally_____________? |
| A. | graphite |
| B. | paper |
| C. | mica |
| D. | insulating varnish |
| Answer» D. insulating varnish | |
| 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. |
The field coils of D.C. generator are usually made of_____________? |
| A. | mica |
| B. | copper |
| C. | cast iron |
| D. | carbon |
| Answer» C. cast iron | |
| 27. |
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 | |
| 28. |
The e.m.f. generated in a D.C. generator is directly proportional to____________? |
| A. | flux/pole |
| B. | speed of armature |
| C. | number of poles |
| D. | all of the above |
| Answer» C. number of poles | |
| 29. |
The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be_____________? |
| A. | 640 V |
| B. | 620 V |
| C. | 600 V |
| D. | 580 V |
| Answer» E. | |
| 30. |
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» C. slightly less than E | |
| 31. |
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 | |
| 32. |
The critical resistance of the D.C. generator is the resistance of_____________? |
| A. | field |
| B. | brushes |
| C. | armature |
| D. | load |
| Answer» B. brushes | |
| 33. |
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 | |
| 34. |
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 | |
| 35. |
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. | |
| 36. |
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 | |
| 37. |
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. | |
| 38. |
Permeance is the reciprocal of______________? |
| A. | flux density |
| B. | reluctance |
| C. | ampere-turns |
| D. | resistance |
| Answer» C. ampere-turns | |
| 39. |
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 | |
| 40. |
Number of tappings for each equalizer ring is equal to_____________? |
| A. | number of pole pairs |
| B. | number of poles |
| C. | number of parallel paths |
| D. | number of commutator segments |
| Answer» B. number of poles | |
| 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» B. permanent magnets | |
| 42. |
Lap winding is composed of_____________? |
| A. | any even number of conductors |
| B. | any odd number of conductors |
| C. | that even number which is exact multiple of poles + 2 |
| D. | that even number which is exact multiple of poles |
| Answer» B. any odd number of conductors | |
| 43. |
Laminations of core are generally made of________________? |
| A. | case iron |
| B. | carbon |
| C. | silicon steel |
| D. | stainless steel |
| Answer» D. stainless steel | |
| 44. |
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 | |
| 45. |
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 | |
| 46. |
Interpole flux should be sufficient to_____________? |
| A. | neutralise the commutating self induced e.m.f. |
| B. | neutralise the armature reaction flux |
| C. | neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil |
| D. | perform none of the above functions |
| Answer» D. perform none of the above functions | |
| 47. |
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. | |
| 48. |
In over compounded generator, full load terminal voltage is______________? |
| A. | almost zero |
| B. | less than no load terminal voltage |
| C. | more than no load terminal voltage |
| D. | equal to no-load terminal voltage |
| Answer» D. equal to no-load terminal voltage | |
| 49. |
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 | |
| 50. |
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 | |