The national grid

• The National Grid is a system of cables and transformers
• The National Grid links all the power stations in the UK to homes and businesses
• Some of the power stations generate electricity all of the time and others are used only when they are needed
• This means customers' electricity demands can be met
• Power stations generate electricity at 25,000 V
• Step-up transformers


  Used at power stations to increase the potential difference from 25,000 V to 132,000 V
• You may have seen electricity pylons in towns and cities
• Many of the cables are hidden underground
• Step-down transformers


  Used to supply electricity from the National Grid to the buyers, decreasing the potential difference to 230 V for homes
• Factories need higher potential differences so the potential difference is decreased to 100,000 V or 33,000 V
• Efficient transfer


  Transformers allow very high potential differences to be used in the National Grid
• A much smaller current is needed to transfer the same amount of energy per second
• A large current would cause the wires in the cables to get very hot
• Using a smaller current means less energy is wasted by being transferred to the thermal store of the cables
• Transformers allow the National Grid to transfer energy in an efficient way
• When you step up the potential difference

  The current decreases
• Parts of the National Grid

  • Step-down transformer
  • Power station
  • Homes
  • Step-up transformer
  • Cables