IGCSE 0625 · ELECTRICITY & MAGNETISM · 4.4

Electrical safety

Common electrical hazards, the wiring of a three-pin plug, how fuses and circuit breakers protect a circuit, and why earthing and double insulation keep us safe. It builds on the electrical quantities and circuits.

TOPIC 4.4: ELECTRICAL SAFETY CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 4.2 Electrical quantities 4.3 Circuits LEADS TO Safe mains use Wiring a plug ELECTRICAL SAFETY 1 · HAZARDS Most electrical dangers come from a few causes. Damaged or frayed insulation exposes live wires. Water and damp let current reach you. Overloaded sockets and coiled cables overheat. Long trailing leads and cracked casings. Pushing objects into sockets. frayed cable: do not use 2 · THE THREE-PIN PLUG A plug connects an appliance to the mains safely. Live (brown) carries the alternating supply. Neutral (blue) completes the circuit. Earth (green and yellow) is a safety path. A fuse sits in the live wire; a grip holds the cable. earth neutral live fuse 3 · FUSES & CIRCUIT BREAKERS A fuse protects the circuit and the cable. A fuse is a thin wire that melts if the current gets too large, breaking the circuit. Choose a rating just above the normal current. A circuit breaker does the same job faster and can be reset instead of replaced. fuse: the thin wire melts and breaks the circuit 4 · EARTHING & DOUBLE INSULATION Earthing stops a metal case becoming live. The metal case is joined to the earth wire. A fault sends a large current safely to earth, which blows the fuse and cuts the supply. Double-insulated appliances have a plastic case and need no earth wire. metal case earth: a fault current flows away
TOPIC 4.4: ELECTRICAL SAFETY CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com BUILDS ON 4.2 Electrical quantities 4.3 Circuits LEADS TO Safe mains use Wiring a plug ELECTRICAL SAFETY 1 · HAZARDS Most electrical dangers come from a few causes. Damaged or frayed insulation exposes live wires. Water and damp let current reach you. Overloaded sockets and coiled cables overheat. Long trailing leads and cracked casings. Pushing objects into sockets. frayed cable: do not use 2 · THE THREE-PIN PLUG A plug connects an appliance to the mains safely. Live (brown) carries the alternating supply. Neutral (blue) completes the circuit. Earth (green and yellow) is a safety path. A fuse sits in the live wire; a grip holds the cable. earth neutral live fuse 3 · FUSES & CIRCUIT BREAKERS A fuse protects the circuit and the cable. A fuse is a thin wire that melts if the current gets too large, breaking the circuit. Choose a rating just above the normal current. A circuit breaker does the same job faster and can be reset instead of replaced. fuse: the thin wire melts and breaks the circuit 4 · EARTHING & DOUBLE INSULATION Earthing stops a metal case becoming live. The metal case is joined to the earth wire. A fault sends a large current safely to earth, which blows the fuse and cuts the supply. Double-insulated appliances have a plastic case and need no earth wire. metal case earth: a fault current flows away
Open the lessons for this topic → Concept map · TheLucidSTEM · thelucidstem.com