These days D.C. motors are widely used in
machine shops
electric traction
pumping sets
air compressors
electric traction
In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
flux is practically constant in D:C. shunt motors
back e.m.f. is equal to armature drop
armature drop is negligible
flux is proportional to armature current
flux is practically constant in D:C. shunt motors
If a D.C. motor is connected across the A.C. supply it will
run at lower speed
not run
run at normal speed
burn due to heat produced in the field winding by .eddy currents
burn due to heat produced in the field winding by .eddy currents
Sparking at the commutator of a D.C. motor may result in
damage to commutator segments
damage to commutator insulation
all of the above
increased power consumption
all of the above
Which of the following motor is preferred for operation in highly explosive atmosphere ?
Air motor
Battery operated motor
Shunt motor
Series motor
Air motor
When two D.C. series motors are connected in parallel the resultant speed is
normal speed
loss than the normal speed
more than the normal speed
zero
normal speed
Which of the following method of speed control of D.C. machine will offer minimum efficiency ?
All above methods
Armature control method
Voltage control method
Field control method
Armature control method
Usually wide and sensitive speed control is desired in case of
colliery winders
centrifugal pumps
elevators
steel rolling mills
colliery winders
In a D.C. shunt motor speed is
inversely proportional to the armature current
proportional to the square of the current
directly proportional to the armature current
independent of armature current
independent of armature current
The ratio of starting torque to full-load torque is least in case of
series motors
compound motors
shunt motors
none of the above
shunt motors
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