Direct Current Machine Or DC Machine Objective Questions and Answers


21.  Air gap at the pole tips of a DC machine is kept more than that at the centre of the pole mainly to reduce


   A. Reactance voltage

   B. Effect of armature reaction

   C. Losses of armature core

   D. Noise of the machine


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B. Effect of armature reaction

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22.  Due to magnetic saturation the flux for pole in a DC machine without brush shift


   A. Increases in both the generators and the motor with load

   B. Decreases in both the generators and the motor with load

   C. Increases in generator but decreases in motors with load

   D. Decreases in generator but decreases in motors with load


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B. Decreases in both the generators and the motor with load

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23.  In a DC machine on no-load the magnetic neutral axis


   A. Moves from geometrical neutral axis in the direction of rotation

   B. Moves from geometrical neutral axis in the opposite direction

   C. Coincides with the geometrical neutral axis

   D. None of the above


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C. Coincides with the geometrical neutral axis

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24.  In a DC machine with out any brush shift, the shift of the magnetic neutral axis owing to armature reaction is


   A. In the direction of rotation for both the generator and the motor

   B. Against the direction of rotation for both the generator and the motor

   C. In the direction of rotation for the generator and against the direction of rotation for the motor

   D. Against the direction of the rotation for the generator and in the direction of rotation off motor


✔ View Answer


C. In the direction of rotation for the generator and against the direction of rotation for the motor

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25.  A P-pole lap wound DC machine had an armature current Ia. The conductor current in the armature winding is


   A. Ia

   B. Ia/P

   C. PIa

   D. None of the above


✔ View Answer


B. Ia/P

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