Mains electricity

  • Created by: Clare
  • Created on: 11-03-13 21:01
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  • Mains Electricity
    • Wiring a plug
      • Blue= neutral
        • Brown= live
          • Yellow/ green= earth
      • Cable grip stops the wires and cables from being pulled out the plug
    • Safety
      • Double insulation
        • As well as the wiring being insulated the plug casing is made of plastic an insulator
        • No chance of electric shock from the casing
      • Insulation
        • This prevents the separate conductors (live, neutral and earth wires) from touching
        • It stops people from touching a live wire
      • Earthing
        • Earth wire provides a very low resistance (so there is a large current which blows the fuse
        • If the live wire touches the metal case current is diverted through the earth wire
        • Current diverts into the earth (soil) which is a good insulator
      • Circuit breakers
        • 'Trip' to disconnect the live supply when a current is exceeded
        • Operated magnetically and can be reset by pressing a button
        • RCCB (residual current circuit breakers)
        • Essential when using appliances in hazardous conditions
        • Mosst appliances break the single switch (live wire) but cookers, showers immersrion heaters are double pole switches (live and neutral wires) for more safety
    • Hazards
      • Frayed cables
        • Damaged insulation exposes 'live' wires
      • Long cables
        • Trip hazard more likely to get damaged
      • Damaged plugs or insulating casting
        • Increase risk of electric shocks
      • Water around sockets
        • When water is next to the skin it becomes a very good conductor
      • Pushing metal into sockets or plugs
        • Metal is an electrical conductor and will cause electric shocks
    • Heating effect
      • USEFUL conversion- into heat
      • Electrical energy in a circuit is converted into other forms
      • E.g.: electric irons, cookers, kettles, hairdryers,
      • If don't want heat, the resistance is made very low
        • If the current that continues to flow in them becomes too great the cables will overheat and may cause a fire
          • This is why fuses are used
    • Power= Current x Voltage
      • Power- watts (W)
        • Current- amps (A)
          • Voltage- volts (V)
      • Use to find correct fuse, need one with a slightly higher CURRENT so rearrange
    • Current
      • Direct Current (DC)
        • Battery makes electricity flow in one direction and has a consistent value
      • Alternating Current (AC)
        • Flows in one direction and then the other e.g.: mains electricity (plug)




Cheers XD

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