Question 456Electricity & Electronics - Assistant Engineer

The correct answer is C. For a shunt wound DC motor, the speed control can be achieved through either armature rheostat control or field rheostat control. In armature rheostat control, increasing the resistance in the armature circuit decreases the motor speed. In field rheostat control, increasing the resistance in the field circuit decreases the field strength, which in turn increases the motor speed. Therefore, the statement in option C accurately describes the relationship between resistance and speed for both armature and field rheostat control. The other options are incorrect because they either reverse the relationship between resistance and speed, or they mix up the effects of armature and field rheostat control.