The correct answer is option 4, electric fuse.

An electric fuse is a safety device that is used in household wiring to prevent accidental fires in case of a short circuit. A short circuit occurs when there is a direct connection between the live wire and the neutral wire, bypassing the normal resistance in the circuit. This can lead to a large flow of current, which can cause overheating and potentially start a fire.

The electric fuse is designed to break the circuit if the current exceeds a certain limit. It consists of a fuse wire made of a material that has a low melting point. When the current exceeds the safe limit, the fuse wire melts, breaking the circuit and stopping the flow of current. This helps to prevent any further damage or risk of fire.

Options 1, 2, and 3 are not correct because they do not directly address the prevention of accidental fires in case of a short circuit. Insulated wire helps in preventing electrical shocks, plastic switches help in controlling the flow of current, and non-metallic coatings on conducting wires help in providing protection against corrosion. While all of these are important for safety in household wiring, they do not specifically prevent fires caused by short circuits.