A Commutator Key is an electrical laboratory instrument used to change or reverse the direction of electric current in a circuit. It consists of brass terminals mounted on an insulated base and is operated manually using a movable key arrangement. The device is widely used in physics laboratories for conducting experiments related to electricity, magnetism, and circuit analysis. Commutator keys are designed to provide smooth switching, reliable contact, and safe operation during experiments. They are commonly used in schools, colleges, and research laboratories for demonstrating current flow and polarity reversal in electrical circuits.