Electrical Machines
A 220 V, DC shunt motor is operating at a speed of 1440 rpm. The armature resistance is 1.0 Ω and armature current is 10 A. of the excitation of the machine is reduced by 10%, the extra resistance to be put in the armature circuit to maintain the same speed and torque will be

 1.79 Ω
 2 .1 Ω
 3.1 Ω
 1.8 9 Ω

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Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 deteriorate with fall of terminal voltage.
 improve with rise in terminal voltage.
 deteriorate with rise in terminal voltage.
 improve with fall of terminal voltage.

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