Practice D.C. Motors Multiple Choice Questions Quiz-2 - MCQGeeks.com

Q.1

Which D.C. motor is preferred for elevators?

Shunt motor
Series motor
Differential compound motor
Cumulative compound motor

Q.2

During rheostatic braking of D.C. series motors

Motor is run as a generator
Motor is reversed in direction
Motor is run at reduced speed
None of these

Q.3

In a D.C. generator all of the following could be the effects of iron losses except

Loss of efficiency
Excessive heating of core
Increase in terminal voltage
Rise in temperature of ventilating air

Q.4

The plugging gives the

Zero torque braking
Smallest torque braking
Highest torque braking
None of the above

Q.5

Which of the following motors one will choose to drive the rotary compressor?

D.C. shunt motor
D.C. series motor
Universal motor
Synchronous motor

Q.6

Following motor is used where high starting torque and wide speed range control is required.

Single phase capacitor start
Induction motor
Synchronous motor
D.C. motor

Q.7

The current drawn by the armature of D.C. motor is directly proportional to

The torque required
The speed of the motor
The voltage across the terminals
None of the above

Q.8

Which D.C. motor will be suitable along with flywheel for intermittent light and heavy loads?

Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor

Q.9

Which of the following motors is most suitable for signaling devices and many kinds of timers?

D.C. shunt motor
D.C. series motor
Induction motor
Reluctance motor

Q.10

D.C. shunt motors are used for driving

Trains
Cranes
Hoists
Machine tools

Q.11

In a manual shunt motor starter

Over load relay is connected in series and no volt relay in parallel with the load
Over load relay is connected in parallel and no volt relay in series with the load
Over load relay and no volt relay are both connected in series with the load
Over load relay and no volt relay are both connected in parallel with the load

Q.12

Sparking, is discouraged in a D.C. motor because

It increases the input power consumption
Commutator gets damaged
Both (A) and (B)
None of the above

Q.13

Why are the D.C. motors preferred for traction applications?

Torque and speed are inversely proportional to armature current
Torque is proportional to armature current
Torque is proportional to square root of armature current
The speed is inversely proportional to the torque and the torque is proportional to square of armature current

Q.14

If I2 be the armature current, then speed of a D.C. shunt motor is

Independent of Ia
Proportional to Ia
Varies as Ia
None of these

Q.15

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

Q.16

In case of conductively compensated D.C. series motors, the compensating winding is provided

As separately wound unit
In parallel with armature winding
In series with armature winding
In parallel with field winding

Q.17

If a D.C. motor is to be selected for conveyors, which rioter would be preferred?

Series motor
Shunt motor
Differentially compound motor
Cumulative compound motor

Q.18

Torque developed by a D.C. motor depends upon

Magnetic field
Active length of the conductor
Current flow through the conductors
All above factors

Q.19

The condition for maximum efficiency for a D.C. generator is

Eddy current losses = stray losses
Hysteresis losses = eddy current losses
Copper losses = 0
Variable losses = constant losses

Q.20

Which of the following motor is preferred for operation in highly explosive atmosphere?

Series motor
Shunt motor
Air motor
Battery operated motor

Q.21

Which method of braking is generally used in elevators?

Plugging
Regenerative braking
Rheostat braking
None of the above

Q.22

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

Q.23

The condition for maximum power in case of D.C. motor is

Back e.m.f. = 2 × supply voltage
Back e.m.f. =1/2 × supply voltage
Supply voltage =1/2 × back e.m.f.
Supply voltage = back e.m.f.

Q.24

In Ward-Leonard control the lower limit of speed is imposed by

Residual magnetism of the generator
Core losses of motor
Mechanical losses of motor and generator together
All of the above

Q.25

Which motor should not be started on no-load?

Series motor
Shunt motor
Cumulatively compounded motor
Differentially compounded motor

Q.26

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

Q.27

D.C. generators are installed near the load centers to reduce

Iron losses
Line losses
Sparking
Corona losses

Q.28

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.

Q.29

The ratio of starting torque to full-load torque is least in case of

Series motors
Shunt motors
Compound motors
None of the above

Q.30

The starting resistance of a D.C. motor is generally

Low
Around 500 Q
1000 Q
Infinitely large

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