51. 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
52. In a D.C. generator the actual flux distribution depends upon
(a) size of air gap
(b) shape of the pole shoe
(c) clearance between tips of the ad¬jacent pole shoes
(d) all of the above
Ans:
53. 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
53. 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
54. 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
55. 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:
56. 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
57. D.C. series generator is used
(a) to supply traction load
(b) to supply industrial load at constant voltage
(c) voltage at the toad end of the feeder
(d) for none of the above purpose
Ans: c
58. Following D.C. generator 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) self-excited generator
Ans: d
59. 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
Ans: c
60. D.C. generator generally preferred for charging automobile batteries is
(a) series generator
(b) shunt generator
(c) long shunt compound generator
(d) any of'the above
Ans: c
(a) E/2
(b) 2E
(c) slightly less than E
(d) E
Ans: b
52. In a D.C. generator the actual flux distribution depends upon
(a) size of air gap
(b) shape of the pole shoe
(c) clearance between tips of the ad¬jacent pole shoes
(d) all of the above
Ans:
53. 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
53. 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
54. 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
55. 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:
56. 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
57. D.C. series generator is used
(a) to supply traction load
(b) to supply industrial load at constant voltage
(c) voltage at the toad end of the feeder
(d) for none of the above purpose
Ans: c
58. Following D.C. generator 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) self-excited generator
Ans: d
59. 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
Ans: c
60. D.C. generator generally preferred for charging automobile batteries is
(a) series generator
(b) shunt generator
(c) long shunt compound generator
(d) any of'the above
Ans: c
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