Question 411Electricity & Electronics - Assistant Engineer

The correct answer is D. The brush holder labeled 4 in the illustration is of the reaction type. Reaction-type brush holders are used in DC motors and generators to maintain contact between the brushes and the commutator as the armature rotates. This design allows the brushes to move in response to the changing position of the commutator, ensuring continuous electrical contact. The other brush holder options (1, 2, and 3) are not of the reaction type, as they do not have the necessary mechanisms to allow the brushes to move in response to the commutator's rotation.