Physics – 4.4 Electrical safety | e-Consult

A fuse protects a circuit and the cabling of a double-insulated appliance by acting as a weak point in the circuit. It is designed to melt and break the circuit if the current becomes too high. This high current can occur due to a fault, such as a short circuit or an overload.

How it protects the circuit: When the current in the circuit exceeds the fuse's rated current, the fuse wire heats up rapidly due to the increased electrical resistance. This heat causes the fuse wire to melt, creating a break in the circuit. This interruption prevents excessive current from flowing throughout the circuit, which could damage components or cause a fire.

How it protects the cabling: Excessive current can also overheat the electrical cables, potentially damaging the insulation and leading to a short circuit or fire. By interrupting the circuit when a fault occurs, the fuse prevents the cables from overheating and becoming damaged. This is crucial for preventing fires and ensuring the safe operation of electrical appliances.

What happens when a fault occurs: A fault can occur in various ways, including:

• Short circuit: This occurs when the live wire comes into direct contact with the neutral wire or the earth wire, creating a low-resistance path for the current.
• Overload: This occurs when too many electrical devices are connected to the same circuit, drawing more current than the circuit is designed to handle.

When a fault occurs, the current in the circuit increases significantly. If the current exceeds the fuse's rated current, the fuse wire melts, breaking the circuit and stopping the flow of electricity.