Question 427Electricity & Electronics - Assistant Engineer

The correct answer is A) The film should be left undisturbed. The chocolate brown film on the copper commutator bars of a DC generator is most likely a natural oxide layer that forms over time. This oxide layer helps to protect the copper from further oxidation and corrosion. Removing this film with abrasives like emery cloth, sandpaper, or emery paper can damage the commutator surface, leading to increased wear and potential issues with electrical conductivity. The best practice is to leave the oxide film undisturbed, as it is not harmful to the generator's operation. Attempting to remove the film could actually do more harm than good, making the answer A the correct choice.