In a conventional DC motor, which component provides the electrical interface between the rotating coil (armature winding) and the external circuit, enabling current reversal each half turn?

Introduction / Context:
DC motors require a mechanism to transfer power from a stationary external circuit to a rotating winding and to reverse the current direction appropriately for continuous torque. Identifying this component is basic electromechanics knowledge.

Given Data / Assumptions:

• Conventional brushed DC motor.
• Rotating armature coil on the rotor.
• Stationary brushes contacting a segmented device on the shaft.

Concept / Approach:
The commutator is a segmented cylindrical switch mounted on the rotor shaft. Stationary carbon brushes press on the commutator, forming the electrical path to the rotating coil and reversing connections every half turn, which keeps torque unidirectional.

Step-by-Step Solution:
Step 1: Identify that current must flow into a rotating winding.Step 2: Recognize that sliding contacts are needed; brushes contact a segmented device.Step 3: Name that device: the commutator, which also provides current reversal timing.

Verification / Alternative check:
By construction, the armature is the winding itself, and the rotor is the rotating assembly that includes the armature and commutator. Only the commutator satisfies the function of switching and providing the sliding electrical interface.

Why Other Options Are Wrong:

• Rotor: Mechanical assembly, not the switching contact device.
• Armature: The winding, not the sliding interface component.
• Battery: External source, not a motor part that performs commutation.
• None of the above: Incorrect because the commutator is correct.

Common Pitfalls:
Some learners attribute the connection role to brushes alone. Brushes are essential, but the commutator provides the segmented switching surface that enables proper current direction in the rotating coil.

Final Answer:
commutator.