What happens to the armature in a DC motor when resistance is added to the circuit?

When resistance is added to the circuit of a DC motor, the current flowing through the circuit is reduced. The armature of the motor relies on this current to generate the magnetic fields necessary for its rotation. As the resistance increases, the amount of current decreases, leading to a reduction in the magnetic force acting on the armature.

This decrease in magnetic force directly impacts the speed at which the armature rotates. With less current, the torque produced by the armature also diminishes, making it harder for the armature to maintain its previous speed. Therefore, the armature speed decreases when additional resistance is introduced into the circuit. This relationship between resistance, current, torque, and speed is fundamental to understanding the operation of DC motors.