DMRC JE/SSC JE/CIL MT ELECTRICAL ENGINEERING IMPORTANT MCQ PART 5(DC MOTORS)

1.In a D.C. shunt motor, speed is
independent of armature current
directly proportional to the armature current
proportional to the square of the current
inversely proportional to the armature current
ANSWER : : independent of armature current
2.The type of D.C. motor used for shears and punches is
shunt motor
series motor
differential compound D.C. motor
cumulative compound D.C. motor
ANSWER : : cumulative compound D.C. motor
3.If a D.C. motor is connected across the A.C. supply it will
run at normal speed
not run
run at lower speed
burn due to heat produced in the field winding by .eddy currents
ANSWER : : burn due to heat produced in the field winding by .eddy currents
4.In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be
almost negligible
rated full-load current
less than full-load current
more than full-load current
ANSWER : : more than full-load current
5.Differentially compound D.C. motors can find applications requiring
high starting torque
low starting torque
variable speed
frequent on-off cycles
ANSWER : : low starting torque 

6.The speed of a D.C. shunt motor more than its full-load speed can be obtained by
decreasing the field current
increasing the field current
decreasing the armature current
increasing the armature current
ANSWER : : decreasing the field current
7.A direct on line starter is used: for starting motors
up to 5 H.P.
up to 10 H.P.
up to 15 H.P.
up to 20 H.P.
ANSWER : : up to 5 H.P.
8.By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
Frame
Shaft
Commutator
Stator
ANSWER : : Commutator
9.These days D.C. motors are widely used in
pumping sets
air compressors
electric traction
machine shops
ANSWER : : electric traction
11.According to Fleming’s left-hand rule,
when the forefinger points in the direction of the field or flux, the
middle finger will point in the direction of
current in the conductor
resultant force on conductor
none of the above
force on the conductor
ANSWER : current in the conductor
12.In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
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
ANSWER : : flux is practically constant in D:C. shunt motors
13.A D.C. series motor is that which
has its field winding consisting of thick wire and less turns
has a poor torque
can be started easily without load
has almost constant speed
ANSWER : : has its field winding consisting of thick wire and less turns
14.When two D.C. series motors are connected in parallel, the resultant speed is
more than the normal speed
loss than the normal speed
normal speed
zero
ANSWER : : more than normal speed
15.If a D.C. motor is to be selected for conveyors, which motor would be preferred ?
Series motor
Shunt motor
Differentially compound motor
Cumulative compound motor
ANSWER : : Series motor 

16.Starters are used with D.C. motors because
these motors have high starting torque
these motors are not self-starting
back e.m.f. of these motors is zero initially
to restrict armature current as there is no back e.m.f. while starting
ANSWER : : to restrict armature current as there is no back e.m.f. while starting
17.Which D.C. motor will be preferred for machine tools ?
Series motor
Shunt motor
Cumulative compound motor
Differential compound motor
ANSWER : : Shunt motor
18.The direction of rotation of a D.C. series motor can be changed by
interchanging supply terminals
interchanging field terminals
either of (a) and (b) above
None of the above
ANSWER : : interchanging field terminals
19.Which of the following application requires high starting torque ?
Lathe machine
Centrifugal pump
Locomotive
Air blower
ANSWER : : Locomotive
20.For starting a D.C. motor a starter is required because
it limits the speed of the motor
it limits the starting current to a safe value
it starts the motor
none of the above
ANSWER : : it limits the starting current to a safe value
21.Which D.C. motor is preferred for elevators ?
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor
ANSWER : : Cumulative compound motor
22.What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
The motor will stop
The motor will continue to run
The armature may burn
The motor will run noisy
ANSWER : : The armature may burn
23.In D.C. shunt motors as load is reduced
the speed will increase abruptly
the speed will increase in proportion to reduction in load
the speed will remain almost constant
the speed will reduce
ANSWER : : the speed will remain almost constant

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DMRC JE/SSC JE/CIL MT ELECTRICAL ENGINEERING IMPORTANT MCQ PART 6(DC MOTORS)
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