61.
In D.C. generators, the brushes on commutator remain in contact with conductorswhich
A
lie under south pole
B
lie under north pole
C
lie under interpolar region
D
are farthest from the poles
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In D.C. generators, the brushes on commutator remain in contact with conductorswhich
lie under south pole
lie under north pole
lie under interpolar region
are farthest from the poles
A D.C. generator works on the principle of
Lenzs law
Ohms law
Faradays law of electromagnetic induction
none of the above
The resistance of armature winding depends on
length of conductor
cross-sectional area of the conductor
number of conductors
all of the above
A D.C. welding generator has
lap winding
wave moving
duplex winding
any of the above
The number of armature parallel paths in a two-pole D.C. generator having duplex lapwinding is
2
4
6
8
Welding generator will have
lap winding
wave winding
delta winding
duplex wave winding
In D.C. generators the polarity of the interpoles
is the same as that of the main pole ahead
is the same as that of the immediately preceding pole
is opposite to that of the main pole ahead
is neutral as these poles do not play part in generating e.m.f.
A separately excited generator as compared to a self-excited generator
is amenable to better voltage con-trol
is more stable
has exciting current independent of load current
has all above features
In a separately excited generator supplying rated load the armature reaction ,
is always present
is always absent
may be sometimes present
none of the above
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in thecoil is neutralised by all of the following except
interpoles
dummy coils
compensating winding
shifting of axis of brushes
In a D.C. generator the critical resistance can be increased by
increasing its field resistance
decreasing its field resistance
increasing its speed
decreasing its speed
In a D.C. generator in case the resistance of the field winding is increased, then outputvoltage will
increase
decrease
remain unaffected
fluctuate heavily
If a D.C. generator fails to build up the probable cause could not be
imperfect brush contact
field resistance less than the critical resistance
no residual magnetism in the generator
faulty shunt connections tending to reduce the residual magnetism
In D.C. generators, lap winding is used for
high voltage, high current
low voltage, high current
high voltage, low current
low voltage, low current
The voltage drop for which of the following types of brush can be expected to be least ?
Graphite brushes
Carbon brushes
Metal graphite brushes
None of the above
The insulating material used between the commutator segments is normally
graphite
paper
mica
insulating varnish
The e.m.f. generated in a D.C. generator is directly proportional to
flux/pole
speed of armature
number of poles
all of the above
A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speedincreases to 1200 r.p.m., the generated e.m.f. will be nearly
150 V
175 V
240 V
290 V
Permeance is the reciprocal of
flux density
reluctance
ampere-turns
resistance
The critical resistance of the D.C. generator is the resistance of
field
brushes
armature
load