Practice D.C. Motors Multiple Choice Questions Quiz-1 - MCQGeeks.com

Q.1

The type of D.C. motor used for shears and punches is

Shunt motor
Series motor
Differential computed D.C. motor
Cumulative compound D.C. motor

Q.2

Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of

D.C. series motor
D.C. shunt motor
Induction motor
All of above motors

Q.3

Hopkinson's test on D.C. machines is conducted at

No load
Part load
Full load
Overload

Q.4

Regenerative method of braking is based on that

Back e.m.f. is less than the applied voltage
Back e.m.f. is equal to the applied voltage
Back e.m.f. of rotor is more than the applied voltage
None of the above

Q.5

Which of the following application requires high starting torque?

Lathe machine
Centrifugal pump
Locomotive
Air blower

Q.6

If the field of a D.C. shunt motor gets opened while motor is running

The speed of motor will be reduced %
The armature current will reduce
The motor will attain dangerously high speed 1
The motor will continue to run at constant speed

Q.7

Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?

Providing laminations in armature core
Providing laminations in stator
Using nonmagnetic material for frame
Using material of low hysteresis coefficient for armature core material

Q.8

The purpose of retardation test on D.C. shunt machines is to find out

Stray losses
Eddy current losses
Field copper losses
Windage losses

Q.9

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

Q.10

To get the speed of D.C, motor below the normal without wastage of electrical energy is used.

Ward Leonard control
Rheostat control
Any of the above method
None of the above method

Q.11

In the D.C. motor the iron losses occur in

The field
The armature
The brushes
The commutator

Q.12

In which of the following applications D.C. series motor is invariably tried?

Starter for a car
Drive for a water pump
Fan motor
Motor operation in A.C. or D.C.

Q.13

In D.C. machines fractional pitch winding is used

To improve cooling
To reduce copper losses
To increase the generated e.m.f.
To reduce the sparking

Q.14

Which of the following loss in a D.C. generator is dissipated in the form of heat?

Mechanical loss
Core loss
Copper loss
All of the above

Q.15

The hysteresis loss in a D.C. machine least depends on

Frequency of magnetic reversals
Maximum value of flux density
Volume and grade of iron
Rate of flow of ventilating air

Q.16

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

Q.17

If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will

Increase
Decrease
Remain same
Become zero

Q.18

In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will

Remain unchanged
Reduce to one-fourth value
Increase four folds
Be doubled

Q.19

Which of the following motors is usually used in household refrigerators?

D.C. shunt motor
D.C. series motor
Single phase induction motor (split phase start or induction run motor)
Reluctance motor

Q.20

Which D.C. motor will be preferred for machine tools?

Series motor
Shunt motor
Cumulative compound motor
Differential compound motor

Q.21

The speed of a D.C. series motor is

Proportional to the armature current
Proportional to the square of the armature current
Proportional to field current
Inversely proportional to the armature current

Q.22

Which of the following law/rule can he used to determine the direction of rotation of D.C. motor?

Lenz
Faraday
Coulomb’s law
Fleming

Q.23

The speed of a D.C. motor can be varied by varying

Field current
Applied voltage
Resistance in series with armature
Any of the above

Q.24

In a differentially compounded D.C. motor, if shunt field suddenly opens

The motor will first stop and then run in opposite direction as series motor
The motor will work as series motor and run at slow speed in the same direction
The motor will work as series motor and run at high speed in the same direction
The motor will not work and come to stop

Q.25

Speed control by Ward Leonard method gives uniform speed variation

In one direction
In both directions
Below normal speed only
Above normal speed only

Q.26

For which types of D.C. motor, dynamic braking is generally used?

Shunt motors
Series motors
Compound motors
All of the above

Q.27

The losses occurring in a D.C. generator are given below. Which loss is likely to have highest proportion at rated load of the generator?

Hysteresis loss
Field copper loss
Armature copper loss
Eddy current loss

Q.28

Which of the following load normally needs starting torque more than the rated torque?

Blowers
Conveyors
Air compressors
Centrifugal pumps

Q.29

As the load is increased the speed of D.C. shunt motor will

Reduce slightly
Increase slightly
Increase proportionately
Remains unchanged

Q.30

The total losses in a well designed D.C. generator of 10 kW will be nearly

100 W
500 W
1000 W
1500 W

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