Which D.C. motor is generally preferred for cranes and hoists ?

Differentially compounded motor

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 aovtaat of conductor

One D.C. motor drives another D.C. motor. The second D.C. motor when excited anddriven

also runs as a motor comes to stop after sometime

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

The speed of a D.C. shunt motor is required to be more than full load speed. This ispossible by

decreasing the armature current

increasing the armature current

increasing the excitation current

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 non-magnetic material for frame

Using material of low hysteresis co-efficient for armature core material

Which D.C. motor has got maximum self relieving property ?

Differentially compounded motor

Which one of the following is not the function of pole shoes in a D.C. machine ?

To spread out flux for better unifor-mity

To reduce the reluctance of the mag-netic path

Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavyloads?

Differentially compounded motor

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

in parallel with armature winding

in series with armature winding

Which of the following motors is usually used in house-hold refrigerators ?

Single phase induction motor (split phase start or induction run motor)

Which motor should not be started on no-load ?

Differentially compounded motor.

61 + Mcqs in Permanent Magnet Dc Pmdc Motors in Electrical Machines Page 1 McqOptions

1.	Which of the following motors one will choose to drive the rotary compressor ?
A.	D.C. shunt motor
B.	D.C. series motor
C.	Universal motor
D.	Synchronous motor
Answer» E.

Discussion

2.	To get the speed of D.C, motor below the normal without wastage of electrical energyis used.
A.	Ward Leonard control
B.	rheostatic control
C.	any of the above method
D.	none of the above method
Answer» B. rheostatic control

Discussion

3.	Which D.C. motor is generally preferred for cranes and hoists ?
A.	Series motor
B.	Shunt motor
C.	Cumulatively compounded motor
D.	Differentially compounded motor
Answer» B. Shunt motor

Discussion

4.	For which of the following applications a D.C. motor is preferred over an A.C. motor ?
A.	Low speed operation
B.	High speed operation
C.	Variable speed operation
D.	Fixed speed operation
Answer» D. Fixed speed operation

Discussion

5.	In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developedby the motor will
A.	remain unchanged
B.	reduce to one-fourth value
C.	increase four folds
D.	be doubled
Answer» B. reduce to one-fourth value

Discussion

6.	Which D.C. motor is preferred for elevators ?
A.	Shunt motor
B.	Series motor
C.	Differential compound motor
D.	Cumulative compound motor
Answer» E.

Discussion

7.	Which of the following motors is most suitable for signalling devices and many kindsof timers ?
A.	D.C. shunt motor
B.	D.C. series motor
C.	Induction motor
D.	Reluctance motor
Answer» E.

Discussion

8.	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
A.	current in the conductor aovtaat of conductor
B.	resultant force on conductor
C.	none of the above
Answer» B. resultant force on conductor

Discussion

9.	One D.C. motor drives another D.C. motor. The second D.C. motor when excited anddriven
A.	runs as a generator
B.	does not run as a generator
C.	also runs as a motor comes to stop after sometime
D.	none
Answer» B. does not run as a generator

Discussion

10.	The mechanical power developed by a shunt motor will be maximum when the ratioof back e.m.f. to applied voltage is
A.	4.0
B.	2.0
C.	1.0
D.	0.5
Answer» E.

Discussion

11.	D.C. generators are installed near the load centres to reduce
A.	iron losses
B.	line losses
C.	sparking
D.	corona losses
Answer» C. sparking

Discussion

12.	D.C. motor is to a drive a load which is almost nil for certain part of the load cycleand peak value for short duration. We will select this
A.	series motor
B.	shunt motor
C.	compound motor
D.	any of the above
Answer» D. any of the above

Discussion

13.	The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. Thespeed regulation of the motor is
A.	2.36%
B.	4.76%
C.	6.77%
D.	8.84%
Answer» C. 6.77%

Discussion

14.	Which of the following law/rule can he used to determine the direction of rotation ofD.C. motor ?
A.	Lenz's law
B.	Faraday's law
C.	Coloumb's law
D.	Fleming's left-hand rule
Answer» E.

Discussion

15.	Why are the D.C. motors preferred for traction applications ?
A.	Torque and speed are inversely proportional to armature current
B.	Torque is proportional to armature current
C.	Torque is proportional to square root of armature current
D.	The speed is inversely proportional to the torque and the torque is proportional to square of armature current
Answer» E.

Discussion

16.	Which of the following motor is preferred for operation in highly explosiveatmosphere ?
A.	Series motor
B.	Shunt motor
C.	Air motor
D.	Battery operated motor
Answer» D. Battery operated motor

Discussion

17.	The speed of a D.C. shunt motor is required to be more than full load speed. This ispossible by
A.	reducing the field current
B.	decreasing the armature current
C.	increasing the armature current
D.	increasing the excitation current
Answer» B. decreasing the armature current

Discussion

18.	As -the load is increased the speed of D.C. shunt motor will
A.	reduce slightly
B.	increase slightly
C.	increase proportionately
D.	remains unchanged
Answer» B. increase slightly

Discussion

19.	Which of the following steps is likely to result in reduction of hysteresis loss in a D.C.generator ?
A.	Providing laminations in armature core
B.	Providing laminations in stator
C.	Using non-magnetic material for frame
D.	Using material of low hysteresis co-efficient for armature core material
Answer» E.

Discussion

20.	B. DC MOTOR1. No-load speed of which of the following motor will be highest ?
A.	Shunt motor
B.	Series motor
C.	Cumulative compound motor
D.	Differentiate compound motor
Answer» C. Cumulative compound motor

Discussion

21.	Which of the following loss in a D.C. generator varies significantly with the loadcurrent ?
A.	Field copper loss
B.	Windage loss
C.	Armature copper loss
D.	None of the above
Answer» D. None of the above

Discussion

22.	Which of the following method of speed control of D.C. machine will offer minimum efficiency ?
A.	Voltage control method
B.	Field control method
C.	Armature control method
D.	All above methods
Answer» D. All above methods

Discussion

23.	Which of the following losses are significantly reduced by laminating the core of aD.C. generator ?
A.	Hysteresis losses
B.	Eddy current losses
C.	Copper losses
D.	Windage losses
Answer» C. Copper losses

Discussion

24.	Which method of braking is generally used in elevators ?
A.	Plugging
B.	Regenerative braking
C.	Rheostatic braking
D.	None of the above
Answer» B. Regenerative braking

Discussion

25.	In a D.C. shunt motor, under the conditions of maximum power, the current in thearmature will be
A.	almost negligible
B.	rated full-load current
C.	less than full-load current
D.	more than full-load current
Answer» E.

Discussion

26.	Which D.C. motor has got maximum self relieving property ?
A.	Series motor
B.	Shunt motor
C.	Cumulatively compounded motor
D.	Differentially compounded motor
Answer» B. Shunt motor

Discussion

27.	Buses, trains, trolleys, hoists, cranes require high starting torque and therefore makeuse of
A.	D.C. series motor
B.	D.C. shunt motor
C.	induction motor
D.	all of above motors
Answer» B. D.C. shunt motor

Discussion

28.	Which one of the following is not the function of pole shoes in a D.C. machine ?
A.	To reduce eddy current loss
B.	To support the field coils
C.	To spread out flux for better unifor-mity
D.	To reduce the reluctance of the mag-netic path
Answer» B. To support the field coils

Discussion

29.	Which of the following tests will be suitable for testing two similar D.C. series motorsof large capacity ?
A.	Swinburne's test
B.	Hopkinson's test
C.	Field test
D.	Brake test
Answer» D. Brake test

Discussion

30.	For which types of D.C. motor, dynamic braking is generally used ?
A.	Shunt motors
B.	Series motors
C.	Compound motors
D.	All of the above
Answer» E.

Discussion

31.	Which of the following motor has the poorest speed regulation ?
A.	Shunt motor
B.	Series motor
C.	Differential compound motor
D.	Cumulative compound motor
Answer» C. Differential compound motor

Discussion

32.	During rheostat braking of D.C. series motors
A.	motor is run as a generator
B.	motor is reversed in direction
C.	motor is run at reduced speed
D.	none
Answer» B. motor is reversed in direction

Discussion

33.	If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?
A.	Series motor
B.	Shunt motor
C.	Differentially compound motor
D.	Cumulative compound motor
Answer» B. Shunt motor

Discussion

34.	Which of the following load normally needs starting torque more than the ratedtorque?
A.	Blowers
B.	Conveyors
C.	Air compressors
D.	Centrifugal pumps
Answer» C. Air compressors

Discussion

35.	If the terminals of armature of D.C. motor are interchanged, this action will offerfollowing kind of braking
A.	regenerative
B.	plugging
C.	dynamic braking
D.	none of the above
Answer» C. dynamic braking

Discussion

36.	For constant torque drive which speed control method is preferred ?
A.	Field control
B.	Armature voltage control
C.	Shunt armature control
D.	Mechanical loading system
Answer» C. Shunt armature control

Discussion

37.	In case-the conditions for maximum power for a D.C. motor are established, theefficiency of the motor will be
A.	100%
B.	around 90%
C.	anywhere between 75% and 90%
D.	less than 50%
Answer» E.

Discussion

38.	Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavyloads?
A.	Series motor
B.	Shunt motor
C.	Cumulatively compounded motor
D.	Differentially compounded motor
Answer» D. Differentially compounded motor

Discussion

39.	Which one of the following is not necessarily the advantage of D.C. motors over A.C.motors ?
A.	Low cost
B.	Wide speed range
C.	Stability
D.	High starting torque.
Answer» B. Wide speed range

Discussion

40.	Following motor is used where high starting torque and wide speed range control isrequired.
A.	Single phase capacitor start
B.	Induction motor
C.	Synchronous motor
D.	D.C. motor
Answer» E.

Discussion

41.	By looking at which part of the motor, it can be easily confirmed that a particularmotor is D.C. motor?
A.	Frame
B.	Shaft
C.	Commutator
D.	Stator
Answer» D. Stator

Discussion

42.	Flywheel is used with D.C. compound motor to reduce the peak demand by the motor,compound motor will have to be
A.	level compounded
B.	under compounded
C.	cumulatively compounded
D.	differentially compounded
Answer» D. differentially compounded

Discussion

43.	Which D.C. motor will be preferred for machine tools ?
A.	Series motor
B.	Shunt motor
C.	Cumulative compound motor
D.	Differential compound motor
Answer» C. Cumulative compound motor

Discussion

44.	The losses occurring in a D.C. generator are given below. Which loss is likely to havehighest proportion at rated load of the generator ?
A.	hysteresis loss
B.	field copper loss
C.	armature copper loss
D.	eddy current loss
Answer» D. eddy current loss

Discussion

45.	In case of conductively compensated D.C. series motors, the compensating winding isprovided
A.	as separately wound unit
B.	in parallel with armature winding
C.	in series with armature winding
D.	in parallel with field winding
Answer» D. in parallel with field winding

Discussion

46.	Which of the following motors is usually used in house-hold refrigerators ?
A.	D.C. shunt motor
B.	D.C. series motor
C.	Single phase induction motor (split phase start or induction run motor)
D.	Reluctance motor
Answer» D. Reluctance motor

Discussion

47.	Which motor should not be started on no-load ?
A.	Series motor
B.	Shunt motor
C.	Cumulatively compounded motor
D.	Differentially compounded motor.
Answer» B. Shunt motor

Discussion

48.	Which of the following application requires high starting torque ?
A.	Lathe machine
B.	Centrifugal pump
C.	Locomotive
D.	Air blower
Answer» D. Air blower

Discussion

49.	PMMDC can only be armature controlled.
A.	True
B.	False
Answer» B. False

Discussion

50.	A PMMDC motor has an armature resistance of 4.2 ohms. When 6 V supply is applied to motor it runs at 1215 rpm drawing 14.5 mA on no-load. The rotational losses is?
A.	86.1 mW
B.	86.1 W
C.	8.6 W
D.	8.6 mW
Answer» B. 86.1 W

Discussion

Explore topic-wise MCQs in Electrical Machines.

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

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

Which D.C. motor is generally preferred for cranes and hoists ?

For which of the following applications a D.C. motor is preferred over an A.C. motor ?

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

Which D.C. motor is preferred for elevators ?

Which of the following motors is most suitable for signalling devices and many kindsof timers ?

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

One D.C. motor drives another D.C. motor. The second D.C. motor when excited anddriven

The mechanical power developed by a shunt motor will be maximum when the ratioof back e.m.f. to applied voltage is

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

D.C. motor is to a drive a load which is almost nil for certain part of the load cycleand peak value for short duration. We will select this

The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. Thespeed regulation of the motor is

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

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

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

The speed of a D.C. shunt motor is required to be more than full load speed. This ispossible by

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

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

B. DC MOTOR1. No-load speed of which of the following motor will be highest ?

Which of the following loss in a D.C. generator varies significantly with the loadcurrent ?

Which of the following method of speed control of D.C. machine will offer minimum efficiency ?

Which of the following losses are significantly reduced by laminating the core of aD.C. generator ?

Which method of braking is generally used in elevators ?

In a D.C. shunt motor, under the conditions of maximum power, the current in thearmature will be

Which D.C. motor has got maximum self relieving property ?

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

Which one of the following is not the function of pole shoes in a D.C. machine ?

Which of the following tests will be suitable for testing two similar D.C. series motorsof large capacity ?

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

Which of the following motor has the poorest speed regulation ?

During rheostat braking of D.C. series motors

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

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

If the terminals of armature of D.C. motor are interchanged, this action will offerfollowing kind of braking

For constant torque drive which speed control method is preferred ?

In case-the conditions for maximum power for a D.C. motor are established, theefficiency of the motor will be

Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavyloads?

Which one of the following is not necessarily the advantage of D.C. motors over A.C.motors ?

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

By looking at which part of the motor, it can be easily confirmed that a particularmotor is D.C. motor?

Flywheel is used with D.C. compound motor to reduce the peak demand by the motor,compound motor will have to be

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

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

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

Which of the following motors is usually used in house-hold refrigerators ?

Which motor should not be started on no-load ?

Which of the following application requires high starting torque ?

PMMDC can only be armature controlled.

A PMMDC motor has an armature resistance of 4.2 ohms. When 6 V supply is applied to motor it runs at 1215 rpm drawing 14.5 mA on no-load. The rotational losses is?