Answer the following questions.

Why is there a key in an electrical circuit?

The key is there in an electrical circuit due to close or open the circuit. When the key is closed the circuit is completed and current flows through the connecting wires. When the key is open the circuit is not completed and the current does not flow through the connecting wires.

If a circuit is connected without a key, there will be a continuous flow of current and the cell may be discharged soon.