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Free download in PDF DC Machines Multiple Choice Questions with Answers for competitive exams. These short objective type questions with answers are very important for competitive exams like IIT-JEE, NEET, AIIMS, JIPMER etc. These short solved questions or quizzes are provided by Gkseries.
61
Frog leg winding is
[A]
Same as simplex winding
[B]
Same as duplex winding
[C]
Combined lap and wave windings on a single rotor
[D]
Duplex wave winding on a single rotor
Answer: Combined lap and wave windings on a single rotor
62
In a compound dc motor, the shunt field winding as compared to series winding will have
[A]
More turns of smaller diameter
[B]
Less turns of larger diameter
[C]
More turns of larger diameter
[D]
Less turns of smaller diameter
Answer: More turns of smaller diameter
63
In dc motor, the amount of flux leakage depends on
[A]
Length of air gap
[B]
Shape of the magnet core
[C]
Flux density used in core and teeth
[D]
All of these
64
The direction of rotation of a dc motor can be reversed by reversing the connection to
[A]
Armature
[B]
Series field
[C]
Shunt field
[D]
Any of the above
65
When an electric traian is moving down a hill the dc motor acts as
[A]
Dc series motor
[B]
Dc shunt motor
[C]
Dc series generator
[D]
Dc shunt generator
Answer: Dc series generator
66
If the armature current of a dc motor is increased keeping the field flux constant, then the developed torque
[A]
Increases proportionately
[B]
Decreases in reverse proportion
[C]
Remains constant
[D]
Increases proportional to the square root of current
Answer: Increases proportionately
67
The armature current drawn by a dc motor is proportional to
[A]
The speed of the motor
[B]
Flux required in the moor
[C]
Torque required
[D]
Voltage applied to the motor
68
A dc shunt motor is driving a constant torque load with rated excitation. If the field current is reduced to half, then the speed of the motor will become
[A]
Half
[B]
Slightly more than half
[C]
Double
[D]
Slightly less than double
Answer: Slightly less than double
69
All d.c. machines are characterized by
[A]
Electric brushes
[B]
Armature
[C]
Commutator
[D]
Magnetic poles
70
Armature voltage control is suitable if d.c. machine is driven at constant
[A]
Torque
[B]
Magnetic field
[C]
Speed
[D]
Current
71
In all electric machines, basic action taking place is
[A]
Motor action
[B]
Generator action
[C]
Both (a) and (b)
[D]
All of these
72
All rotating machines are basically
[A]
D.C. machines
[B]
A.C. machines
[C]
Electro-mechanical convertors
[D]
Heat converters
Answer: Electro-mechanical convertors
73
All machines have the structure such that
[A]
Armature is rotating and field is fixed
[B]
Field is rotating and armature is fixed
[C]
Either (a) or (b)
[D]
None of these
Answer: Armature is rotating and field is fixed
74
Maximum number of brushes which can be used in a machine is
[A]
2
[B]
4
[C]
6
[D]
Number of poles in the machine or 2
Answer: Number of poles in the machine or 2
75
Voltage applied across the shunt motor has to
[A]
Overcome the back emf
[B]
Supply armature ohmic drop
[C]
Supply fied ohmic drop
[D]
Both (a) and (b)
76
If field of d.c. shunt motor is opened, then
[A]
Current in the armature will increase
[B]
It will run at its normal speed
[C]
Speed of motor will be reduced
[D]
Speed of motor will be high
Answer: Speed of motor will be high
77
Which of the following motors has high starting torque?
[A]
D.C. shunt motor
[B]
Induction motor
[C]
D.C. series motor
[D]
A.C. series motor
Answer: D.C. series motor
78
Left hand rule is applicable to
[A]
Motor
[B]
Generator
[C]
Transformer
[D]
Mercury are rectifier
79
A dc series motor is running with a diverter connected across its field winding. If the diverter resistance is increased, then the speed of the motor
[A]
Decreases/increase
[B]
Increase
[C]
Remains unchanged
[D]
Becomes very high
Answer: Decreases/increase
80
A dc series motor is running at rated speed. If a resistance is placed in series, the speed of the motor
[A]
Increases
[B]
Decreases
[C]
Remains unchanged
[D]
Increases very much
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