D.C. Generators Multiple Choice Questions And Answers In English -03

1. A D.C. generator can be considered as
(A) rectifier
(B) prime mover
(C) rotating amplifier
(D) power pump
Ans: C

2. In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called
(A) rotor
(B) stator
(C) field
(D) armature
Ans: D

3. In a D.C. machine stray loss is the sum of
(A) total copper loss and mechanical loss
(B) armature copper loss and iron loss
(C) shunt field copper loss and mechanical loss
(D) iron loss and mechanical loss
Ans: D

4. 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
Ans: A

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
Ans: B

6. 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
Ans: D

7. In a D.C. generator the critical resistance refers to the resistance of
(A) brushes
(B) field
(C) armature
(D) load
Ans: B

8. 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
Ans: B

9. 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
Ans: B

10. 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
Ans: C

11. 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
Ans: B

12. The material for commutator brushes is generally
(A) mica
(B) copper
(C) cast iron
(D) carbon
Ans: D

13. 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 equalizer rings
Ans: C

14. The insulating material used between the commutator segments is normally
(A) graphite
(B) paper
(C) mica
(D) insulating varnish
Ans: C

15. 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
Ans: C

16. 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) cross magnetisation as well as demagnetising
(D) cross magnetisation only
Ans: C

17. Armature reaction of an unsaturated D.C. machine is
(A) cross magnetising
(B) demagnetising
(C) magnetising
(D) none of above
Ans: A

18. 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 equalizer rings
Ans: C

19. D.C. generators are connected to the busbars or disconnected from them only under the floating condition
(A) to avoid sudden loading of the prime mover
(B) to avoid mechanical jerk to the shaft
(C) to avoid burning of switch contacts
(D) all above
Ans: D

20. 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
Ans: D