2.3 describe the uses of insulation, double insulation, earthing, fuses and circuit breakers in a range of domestic appliances

Insulation –

  • All mains wiring is double insulated (meaning there are two layers of insulation)
  • This prevents the separate conductor wires (live, neutral and earth) from touching
  • This also protects other people from touching electrically charged wires

Double insulation –

  •  As well as the wiring within the plug being insulated, the outer cast is insulated by plastic
  • This means little to no electrical shocks
  • This insulatory method is used in kettles and electric drills

Earthing –

  • By ensuring that the outer metal casing of the appliance has no charge, it makes the appliance safe to touch
  • The fault current allows this to happen will be very large and cause the fuse wire to blow immediately, causing a disconnection from the live supply

Fuses – 

  • Fitted in plugs, ceramic cartridge fuses have heat proof tubes containing a wire designed to melt when a specific current size is met or exceeded
  • This cuts off the live supply (by melting) and will have to be replaced once blown

Circuit breakers –

  • Used in domestic consumer units and do the same job as fuses by breaking the live connecting when a specific current size is exceeded, but in industry it is operated by magnets and buttons
  • RCBS – Residual Circuit Breakers – designed to disconnect the live supply at much lower current levels

Switch –

  • Single pole switches – Breaks the live wire in the circuit
  • Double pole switches – Breaks the live and neutral wire for extra safety.




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