The National Grid: Electricity: Physics: GCSE (9:1)

• National Grid

  A system of cables and transformers linking power stations to consumers

  
• What the National Grid does

  Connects power stations to homes, workplaces and public buildings all around the country

  
• Transformer


  An electrical device that changes the potential difference of an alternating current

  
• Structure of a transformer


  Two coils of wire wrapped around a magnetic core

  
• Step-up transformer

  A transformer used to increase the potential difference from the power station to the transmission cables

  
• Step-down transformer

  A transformer used to decrease the potential difference to a much lower value for domestic use

  
• Generator

  A device found in power stations that transfers kinetic energy to electrical energy

  
• Transmission lines

  Cables used to carry electricity long distances via the National Grid

  
• Energy dissipated by transmission lines

  wasted energy transferred to the surroundings due to an electric current flowing through the cables and causing them to get hotter

  
• P = I²R


  The equation linking power (dissipated), current and resistance

  
• How to reduce the energy dissipated from transmission lines

  1) thick cables which have a low resistance

  2) high potential difference to reduce the current passing through them
• 25,000 V


  The potential difference of the electricity produced in power stations

  
• 400,000 V


  The potential difference that electricity is stepped to before it is transmitted across the country

  
• 230 V


  The potential difference that electricity is stepped down to before it is delivered to houses