Electricity

• Main supply

  The electricity that comes from the national grid, which is an alternating current of 230 volts at 50 hertz
• Three core cable

  • Contains a live wire, a neutral wire, and an earth wire
• Live wire

  Brown wire that provides the alternating potential difference of around 230 volts from the main supply
• Neutral wire

  Blue wire that acts to complete the circuit by carrying away current
• Earth wire

  Striped green and yellow wire that doesn't normally carry a current and has a potential difference of zero volts, its role is to stop the appliance casing from becoming live
• Live wire at 230 volts

  Electricity passes through the neutral wire or earth wire which have a potential difference of zero volts
• Humans have a potential difference of zero volts

  Touching the live wire will cause a large current to flow through us in the form of an electric shock
• It's important to never touch plug sockets even if they're switched off, as the live wire still has a potential difference and any contact could result in a shock
• Surge

  Sudden increase in current
• Causes of surges

  1. Changes in a circuit like turning an appliance on or off

  2. Faults in the circuit or appliance
• Surges

  Can damage appliances, cause fires, or electric shocks
• Safety precautions to reduce risks from surges

  • Fuses
  • Circuit breakers
  • Earth wires
  • Double insulation
• Fuse

  A very thin piece of wire connected to the live wire that melts when there is a surge, breaking the circuit
• Fuses

  • Simple and cheap
  • Permanently broken after a single surge, need to be replaced
• Circuit breaker

  Breaks the circuit when there is a surge, but can be reset rather than replaced
• Circuit breakers

  • More expensive than fuses
• Earthing

  An earth wire provides an alternative pathway for current to flow away, diverting it from the user
• Double insulation

  The entire appliance is covered in a plastic casing so there are no exposed metal parts that can conduct electricity
• Appliances with double insulation do not need an earth wire, they just have a live and neutral wire