Electrical Machines
Armature reaction in a DC machine

  makes an angle of 90° with the main pole axis.
 is in direct opposition to the main poles.
 is in the same direction as the main poles.
 makes an angle with the main pole axis which is load dependent.

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Electrical Machines
In a dc generator operating on load with its brushes on the geometrical neutral axis (GNA), the magnetic neutral axis (MNA) is shifted in the direction of rotation. Now, if the brushes are given a lead of 90° (electrical), then the MNA will

 coincide with the GNA
 shift forward by more than 90°
 shift forward by 90°
 shift forward by less than 90°

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