Common Hazards -

  1. Damaged Insulation - Touching exposed wire
  2. Overheating - Too much current in a small wire = fire/melting insulations
  3. Damp Conditions - Conduction through water → short circuit and electrocution risk
  4. Excess current from overloading of plugs, extension leads, single and multiple sockets when using a mains supply - if this happens heat can cause fire

A mains circuit consists of a live wire (line wire), a neutral wire and an earth wire and explain why a switch must be connected to the live wire for the circuit to be switched off safely - Explanation: A switch must be connected in the live wire so that when it is in 'off' position, the circuit is incomplete and no current reaches the appliance through the live wire.

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Protection Means -

  1. Insulation - prevents direct contact with the live wire
  2. Double insulation - no earthing wire req
    1. Insulation around main wire
    2. Non-metallic case acting as secondary layer
  3. Earthing -
    1. Many appliances have metal casing, hence Earth wire is needed connecting metal casing to earth
    2. Earthing wire → provides lowest resistance path to earth, hence any current in the casing goes to earth
  4. Fuse -
    1. Consists of glass cylinder with thin metal wire, when current becomes too much wire melts stopping current breaking circuit
    2. Trip switch does the same
    3. FUSES ALWAYS HAVE TO BE HIGHER THAN CURRENT NEEDED BUT NOT TOO HIGH

State that a fuse without an earth wire protects the circuit and the cabling for a double-insulated appliance - The fuse prevents electrical hazards by interrupting the circuit in case of an overload or short circuit, ensuring safety in the absence of an earth connection in such appliances.