At the instant of starting when a D.C. motor is put on supply, it behaves like

Solution(By Examveda Team)

At the instant of starting, when a D.C. motor is put on supply, it initially behaves like a highly resistive circuit. This behavior is primarily due to the low resistance of the armature windings and brushes, which offer minimal opposition to the flow of current. As a result, the motor draws a high starting current, often several times higher than its rated current, to overcome the initial inertia and start rotating.

This high starting current, combined with the low resistance of the circuit, results in a situation akin to a highly resistive circuit. As the motor gains speed and reaches its operating condition, the resistance decreases, and the motor settles into its normal operating state.

Options B and C are incorrect because:
Option B: A low resistance circuit implies minimal opposition to the flow of current, which is not characteristic of a D.C. motor at the instant of starting.
Option C: A capacitive circuit involves the storage and release of electrical energy in a capacitor, which is not relevant to the behavior of a D.C. motor at startup.

Therefore, the correct answer is Option A: A highly resistive circuit, as this best describes the initial behavior of a D.C. motor when it is put on supply.