In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except______________?

Related Mcqs:

1. 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

2. 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

3. Armature coil is short circuited by brushes when it lies_____________?

   A. along neutral axis
   B. along field axis
   C. in any of the above positions
   D. in none of the above positions

4. 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

5. 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

6. 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

7. 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

8. If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be____________?

   A. zero
   B. small
   C. the same as rated voltage
   D. high

9. 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

10. A shunt generator can self-excite:_________________?

    A. only if the resistance of the field circuit is less than critical value
    B. only if the resistance of the field circuit is greater than critical value
    C. irrespective of the value of the resistance in the field circuit
    D. none