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

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

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Electrical Machines
The speed of a DC series motor is

 Proportional to the square of the armature current.
 Inversely proportional to the armature current.
 Proportional to field current.
 Proportional to the armature current.

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