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18 questions
____ is followed to determine the direction of coil movement for electric motors
Fleming's left hand rule
Faraday's left hand rule
Faraday's right hand rule
Fleming's right hand rule
What does the thumb indicate in Fleming's left hand rule
Force
Current
Magnetic field
Voltage
What is the direction of coil movement in the image shown
Towards the magnet
Away from the magnet
In the direction of current flow
Downwards
Choose all that applies to a DC Shunt motor
Field winding has more number of turns of thin wires
High starting torque
Constant Speed Motor
Used in electric cars
A d.c. generator whose field magnet winding is supplied from an independent external d.c. source:
Self Excited DC generator
Separately excited DC generator
The direction of the induced emf in generators is found out using:
Fleming's right hand rule
Fleming's left hand rule
Faraday's left hand rule
Right hand thumb rule
Speed of the induction motor reduces with the load applied
True
False
The difference between the speed of the stator and the actual speed is called
____ is used to provide electrical connectivity between the static and rotating parts of the DC motor
Commutator
Brush
Force acting on the conductor is proportional to the current in the conductor and the strength of the magnetic field
True
False
Why does the torque and armature current characteristics of a DC shunt motor take a linear relationship?
Due to constant flux
Due to constant armature current
Due to variations in the flux with changes in supply voltage
Because the armature current is varied accordingly
It is difficult to start a DC shunt motor on heavy loads:
Due to large starting current requirement
Due to large starting voltage requirement
The residual flux present during the start of the motor is not sufficient
Under normal conditions the flux and the back emf of a DC shunt motor are constant
True
False
For a DC Shunt motor, the speed and torque characteristic is approximately similar to Torque and Armature current characteristics.
True
False
Which motor has high starting torque
DC Series Motor
DC Shunt Motor
Which motor develops high starting torques at low speeds and low torque at high speeds
DC Series Motor
DC Shunt Motor
In DC Series motor the field flux becomes independent of the armature current after it reaches a saturation point
True
False
For A DC series motor, the speed may become dangerously high if load reduces to a small value. So,
It must not be run on no load
It must not be run on less load at high currents
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