DC Generator Questions and Answers | Online Quiz for Practice

46. A D.C. generator works on the principle of

1. Lenzs law
2. Ohms law
3. Faradays law of electromagnetic induction
4. none of the above

47. In D.C. generators, the brushes on commutator remain in contact with conductorswhich

1. lie under south pole
2. lie under north pole
3. lie under interpolar region
4. are farthest from the poles

48. Flemings right-hand rule regarding direction of induced e.m.f., correlates

1. magnetic flux, direction of current flow and resultant force
2. magnetic flux, direction of motion and the direction of e.m.f. induced
3. magnetic field strength, induced voltage and current
4. magnetic flux, direction of force and direction of motion of conductor

49. Compensating windings are used in D.C. generators

1. mainly to reduce the eddy currents by providing local short-circuits
2. to provide path for the circulation of cooling air
3. to neutralise the cross-magnetising effect of the armature reaction
4. none of the above

50. The field coils of D.C. generator are usually made of

1. mica
2. copper
3. cast iron
4. carbon

51. The material for commutator brushes is generally

1. mica
2. copper
3. cast iron
4. carbon

52. The terminal voltage of a series generator is 150 V when the load current is 5 A. If theload current is increased to 10 A, the terminal voltage will be

1. 150 V
2. less than 150 V
3. greater than 150 V
4. none of the above

53. According to Flemings 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

1. motion of conductor
2. lines of force
3. either of the above
4. none of the above

54. In the case of lap winding resultant pitch is

1. multiplication of front and back pitches
2. division of front pitch by back pitch
3. sum of front and back pitches
4. difference of front and back pitches

55. In a level compounded D.C. generator, full load terminal voltage is

1. negligibly low
2. equal to no-load terminal voltage
3. more than no-load terminal voltage
4. less than no-load terminal voltage

56. Interpole flux should be sufficient to

1. neutralise the commutating self induced e.m.f.
2. neutralise the armature reaction flux
3. neutralise both the armature reaction flux as well as commutating e.m.f. induced in thecoil
4. perform none of the above functions

57. Flashing the field of D.C. generator means

1. neutralising residual magnetism
2. creating residual magnetism by a D.C. source
3. making the magnetic losses of forces parallel
4. increasing flux density by adding extra turns of windings on poles

58. In case of D.C. machine winding, number of commutator segments is equal to

1. number of armature coils
2. number of armature coil sides
3. number of armature conductors
4. number of armature turns

59. Number of tappings for each equilizer ring is equal to

1. number of pole pairs
2. number of poles
3. number of parallel paths
4. number of commutator segments

60. A series generator can self-excite

1. only if the load current is zero
2. only if the load current is not zero
3. irrespective of the value of load current
4. none of the above