NEIEP Mechanics Practice Exam

What component primarily determines the direction of current in a DC motor?

1. Commutator

2. Field winding

3. Armature

4. Brushes

The correct answer is: Commutator

The commutator plays a crucial role in determining the direction of current in a DC motor. In a DC motor, the commutator is a split ring device that reverses the direction of current flowing through the armature windings every half turn. This reversal of current is essential for maintaining continuous rotation in a single direction, allowing the motor to operate effectively. When current flows through the armature windings, it interacts with the magnetic field produced by the field winding. The resulting electromagnetic force generates torque, causing the armature to rotate. As the armature spins, the commutator ensures that the direction of the current in the windings flips at the appropriate moments, thus keeping the torque in the same rotational direction. Without the commutator's action of reversing the current, the motor would not be able to sustain its motion. Field windings, while important for creating the magnetic field, do not change the direction of current; instead, they provide a constant magnetic field. The armature is where the current is induced and where torque is produced, but it is the commutator that actively changes the current direction. Brushes are used to conduct current to the rotating armature via the commutator but do not influence the current's