NEIEP Mechanics Practice Exam

In a DC generator, what component is used for switching the current?

1. Transformer

2. Commutator

3. Rectifier

4. Inductor

The correct answer is: Commutator

In a DC generator, the component responsible for switching the current is the commutator. The commutator is a mechanical switch that reverses the direction of current flow in the winding of the generator as it rotates. This action allows the generator to produce direct current (DC) instead of alternating current (AC). As the coils in the generator rotate within the magnetic field, they induce an alternating current due to electromagnetic induction. The commutator takes this alternating current and effectively rectifies it into direct current by switching the connections of the winding to the external circuit at the appropriate moments, ensuring a continuous flow of current in one direction. This is essential for the functioning of DC generators. The other options contribute to different electrical functions and systems. A transformer is used to change the voltage level in AC systems, a rectifier converts AC to DC but is not a mechanical component, and an inductor stores energy in a magnetic field when current flows through it but does not switch current direction. Thus, the commutator's role in current switching is central to the operation of a DC generator.