Fuses and Earthing

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Earthing and Fuses

  • prevent electrical overloads
  • if a fault develops and the live wire touches the metal case because the case is earthed too great a current flows through the live wire, into the case and out of the earth wire. This surge in current melts the fuse if the current is greater than the fuse rating, This cuts off the live supply and breaks the circuit.
  • Earthing isolates the appliance and stops you getting an electric shock from the case. It also stops the risk of there being a fire.
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  • Fuses are also therer to stop the appliances from getting too damaged from from a current surge as it protects the circuits and the wiring
  • They should be rated as near as possible but just higher than the normal operating current
  • the larger the current, the thicker the cable. Usually as the fuse rating increases so does the thikness of the cable.
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Double Insulating

  • All appliances that have metal cases are earthed, this reduces the danger of an electric shock.
  • An earthed conductor can never become live.
  • If an appliance has a plastic casing and no metal parts showing it is said to be double insulated
  • Anything that is double insulated doesn't need an earth wire
  • Cables that only have a live and neutral wire are called two-core cables
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