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GCSE Combined Science · key term
A safety device containing a wire that heats up and melts when the current becomes too large, breaking the circuit.
Used by Edexcel
Paper 5, Paper 6
Revise: A.c., d.c. and mains electricity safetyA fuse contains a thin wire. If the current becomes too large, the wire heats up and melts, breaking the circuit. In this fault, the large current causes the fuse in the live wire to melt, disconnecting the appliance from the live supply.
For an earthing explanation, link each step: live wire touches metal case → current flows through the low-resistance earth path → fuse melts or circuit breaker trips → live supply is disconnected.
Explain that a switch or fuse in the neutral wire could stop the current while leaving the appliance connected to the live supply.
Do not describe the neutral wire as always safe to touch, or assume that a fuse prevents every electric shock.
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