What elements make up commutator film?

The correct choice highlights the composition of commutator film as being made up of a combination of copper oxide film, graphite film, free graphite particles, and water vapor components. This composition is critical to the function of commutators in electrical machines, as it contributes to reducing friction and wear during the operation of the components.

Copper oxide forms on the commutator surface due to oxidation and aids in electrical conduction, while the graphite provides lubrication, which is essential for smooth contact between the brushes and the commutator. The presence of free graphite particles enhances this lubricating effect, ensuring that the performance of the commutator is optimized, ultimately prolonging its lifespan and improving efficiency.

Moisture in the form of water vapor can also play a role as it sometimes assists in the formation of a stable film, which can improve the electrical characteristics of the interface. Proper management of this film is vital in maintaining the overall effectiveness of the commutation process in electric motors and generators.

In contrast, the other choices do not adequately represent the elements that typically comprise commutator film. For instance, aluminum oxide and oil refer to different contexts involving lubrication and corrosion resistance in other applications, while silicon, copper, and iron lack direct relevance to the specific