Electricity in the Home

• Alternating current (ac)


  1. Current is constantly changing direction

  2. Alternating potential difference in which the positive and negative ends keep alternating
• UK mains supply


  ac supply at around 230 V
• Frequency of ac mains supply

  50 cycles per second or 50 Hz
• Direct current (dc)


  • Current that is always flowing in the same direction
  • Created by a direct potential difference
• Types of electricity supplies

  • Alternating current (ac)
  • Direct current (dc)
• Most electrical appliances


  • Connected to the mains supply by three-core cables
  • Have three wires inside them, each with a core of copper and a coloured plastic coating
• Colours of insulation on each cable

  • Blue (neutral wire)
  • Brown (live wire)
  • Green and yellow (earth wire)
• Neutral wire


  Completes the circuit when the appliance is operating normally, current flows through the live and neutral wires, around 0V
• Live wire


  Provides the alternating potential difference (at about 230 V) from the mains supply
• Earth wire


  For protecting the wiring, and for safety it stops the appliance casing from becoming live, doesn't usually carry a current, also at 0V
• Touching the live wire


  Gives you an electric shock
• Even if a plug socket or a light switch is turned off (i.e. the switch is open) there is still a danger of an electric shock
• Any connection between live and earth can be dangerous, if the link creates a low resistance path to earth, a huge current will flow, which could result in a fire