D.C. Generators Multiple Choice Questions And Answers In English -02

1. Welding generator will have
(A) lap winding
(B) wave winding
(C) delta winding
(D) duplex wave winding
Ans: A

2. 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
Ans: A

3. 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
Ans: C

4. 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
Ans: D

5. 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
Ans: D

6. A D.C. welding generator has
(A) lap winding
(B) wave moving
(C) duplex winding
(D) any of the above
Ans: A

7. 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
Ans: A

8. Brushes of D.C. machines are made of
(A) carbon
(B) soft copper
(C) hard copper
(D) all of above
Ans: A

9. The armature core of a D.C. generator is usually made of
(A) silicon steel
(B) copper
(C) non-ferrous material
(D) cast-iron
Ans: A

10. 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
Ans: D

11. 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
Ans: C

12. In a D.C. machine, fractional pitch winding is used
(A) to increase the generated voltage
(B) to reduce sparking
(C) to save the copper because of shorter end connections
(D) due to (B) and (C) above
Ans:

13. For the parallel operation of two or more D.C. compound generators, we should ensure that
(A) voltage of the incoming generator should be same as that of bus bar
(B) polarity of incoming generator should be same as that of bus bar
(C) all the series fields should be run in parallel by means of equilizer connection
(D) series fields of all generators should be either on positive side or negative side of the armature
(e) all conditions mentioned above should be satisfied
Ans: D

14. If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by
(A)Blv
(B)Blv2
(C)Bl2v
(D)Bl2v2
Ans: A

15. 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
Ans: B

16. In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when
(A) r.p.m. is more than 300
(B) r.p.m. is less than 300
(C) number of poles is 4
(D) number of poles is 2
Ans: D

17. Permeance is the reciprocal of
(A) flux density
(B) reluctance
(C) ampere-turns
(D) resistance
Ans: B

18. In D.C. generators the polarity of the interpoles
(A) is the same as that of the main pole ahead
(B) is the same as that of the immediately preceding pole
(C) is opposite to that of the main pole ahead
(D) is neutral as these poles do not play part in generating e.m.f.
Ans: A

19. 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
Ans: B

20. In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when
(A) there is no load on|he generator
(B) the generator runs on full load
(C) the generator runs on overload
(D) the generator runs on designed speed
Ans: A