2 - ELECTRICITY

Safe plugs 

• Right coloured wire connected to each pin 
• Wires screwed in 
• No bare wires 
• Cable grip fastened over outer layer - holds all wires in place 
• Metal parts = copper or brass (very good conductors) 
• Case/cable grip/cable insulation = rubber or plastic (good insulators, flexible) 

Earthed/insulated - 

• Live wire - alternates between high +ve and -ve voltage (about 230V) 
• Neutral wire - 0V 
• Electricity flows through live wire and out neutral wire (normally) 
• Earth wire and fuse/circuit breaker - safety, work together 

1. Fault in live wire 
2. Touches metal case of an appliance - case is earthed 
3. Flows through case and down earth wire (not someones hand etc.) 
4. Surge in current melts fuse - cuts off live supply 
5. Isolates whole appliance - can't get electric shock from case 
6. No risk of fire - no heating from effect of even larger current 

Circuit breakers - 

• Circuit breakers - electrical safety device, protect circuit from damage if too much current flows 
• Detect surge in current - break circuit by opening a switch 
• Can be reset easily (unlike fuses - need to be replaced) 
• Faster then fuse - break current as soon as there is a current surge, don't wait to be melted (safer) 
• Work for even small current changes 
• eg: RCCB (residual current circuit breaker)

Safety precautions with plugs - 

• Check plug isn't damaged - live parts could be exposed 
• Check cable isn't frayed - live parts of wires could be exposed 
• Check cables aren't too long for appliance - trip hazard 
• Check there's no water nearby - good conductor 
• Don't put metal in plug socket - conductors