In the D.C. motor the iron losses occur in
the commutator
the armature
the field
the brushes
the armature
The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by
reducing the field current
decreasing the armature current
increasing the armature current
increasing the excitation current
reducing the field current
One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven
none
also runs as a motor comes to stop after sometime
does not run as a generator
runs as a generator
runs as a generator
For the same H.P. rating and full load speed following motor has poor starting torque
shunt
series
differentially compounded
cumulativelyc’ompounded
differentially compounded
When the armature of a D.C. motor rotates e.m.f. induced is
back e.m.f.
none of the above
mutually induced e.m.f.
self-induced e.m.f.
back e.m.f.
In case of conductively compensated D.C. series motors the compensating winding is provided
in series with armature winding
in parallel with armature winding
as separately wound unit
in parallel with field winding
in series with armature winding
If the supply voltage for a D.C. motor is increased which of the following will decrease ?
All of the above
Full-load current
Starting torque
Operating speed
Full-load current
The mechanical power developed by a shunt motor will be maximum when the ratio of back e.m.f. to applied voltage is
0.5
4
2
1
0.5
The condition for maximum power in case of D.C. motor is
supply voltage = back e.m.f.
supply voltage = | x back e.m.f.
back e.m.f. = 2 x supply voltage
back e.m.f. = | x supply voltage
back e.m.f. = | x supply voltage
For which of the following applications a D.C. motor is preferred over an A.C. motor ?
Low speed operation
High speed operation
Variable speed operation
Fixed speed operation
Variable speed operation
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