A fuse is a safety device used in an electric circuit to protect the circuit and the connected devices from damage. When excessive current flows through the circuit, the fuse is designed to break the circuit by melting its fuse element. This helps to prevent overheating and potential fire hazards caused by the excessive flow of current.

Option 1 is the correct answer because it accurately describes the purpose of a fuse. When the current reaching the circuit exceeds the capacity of the fuse, it melts and breaks the circuit, thereby protecting the devices and preventing further damage.

Option 2 is incorrect because a fuse does not break the circuit when the power gets turned off. It only breaks the circuit when there is excessive current flow.

Option 3 is incorrect because a fuse does not indicate if the current is flowing uninterrupted. It is a protective device that breaks the circuit when there is excessive current flow.

Option 4 is incorrect because a fuse does not complete the circuit for the flow of current. It is designed to break the circuit under specific conditions to protect the circuit and connected devices.

Therefore, the correct answer remains option 1.