Electricity in the Home

• There are 2 types of electricity supply - alternating and direct currents
• Mains supply is ac, battery supply is dc
• In ac supplies the current is constantly changing direction
• Alternating currents are produced by alternating voltages in which the positive and negative ends keep alternating
• The UK mains supply (electricity in your home) is an ac supply at around 230 V
• Cells and batteries supply direct current (dc)
• Direct current is a current that is always flowing in the same direction. It's created by direct voltage
• Most cables have 3 separate wires
• Most electrical appliances are connected to the mains supply by three-core cables. This means that they have 3 wires inside them, each with a core of copper and a coloured plastic coating
• The colour of the insulation on each cable shows its purpose
• The colours are always the same for every appliance. This is so that it is easy to tell the different wires apart
• Live wire - brown

  The live wire provides the alternating potential difference (at about 230 V) from the mains supply
• Live wire - brown

  The live wire provides the alternating potential difference (at about 230 V) from the mains supply

  
• Neutral wire - blue

  The neutral wire completes the circuit - when the appliance is operating normally, current flows through the live and neutral wires. It's around 0 V

  
• Earth wire - green and yellow

  It's for protecting the wiring, and for safety - it stops the appliance casing from becoming live. It doesn't usually carry a current - only when there's a fault. It is at 0 V
• The live wire can give you and electric shock
• Your body just like the earth, is at 0 V. This means that if you touch the live wire, a large potential difference is produced accross your body and a current flows through you. This causes an electric shock which could injure you or even kill you
• 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. A current isn't flowing but there's still a pd in the wire
• If you made contact with the live wire, your body would provide a link between the supply and the earth, so a current would flow through you
• 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