Fuses are used in some electrical circuits for safety - Junior Cycle Science - Question g - 2012

A fuse is a safety device used in electrical circuits, and it operates based on the principles of thermodynamics and electrical resistance. When the current flowing through the circuit exceeds a predetermined limit, typically due to a fault such as a short circuit or overload, the heat generated by the excessive current causes the metal wire inside the fuse to melt.

Once the wire melts, it breaks the circuit, stopping the flow of electricity. This disconnection prevents further damage to the electrical components and significantly reduces the risk of fire or electric shock, ensuring the safety of both the circuit and the users.

In essence, the fuse acts as a protective element, limiting the amount of current that can pass through. If the current exceeds the safe threshold, the fuse blows, thereby providing an essential safety mechanism in electrical systems.