The National Grid (AQA GCSE Combined Science: Trilogy: Physics): Revision Note

The National Grid

• The National Grid distributes electricity across the UK

  • It consists of a system of cables and transformers linking power stations to consumers (houses, factories and buildings)

• Electrical power is transferred from power stations to consumers using the National Grid

• The transformers include:

  • Step-up transformers, at the power station, increase the potential difference (and decrease the current) from the power station to the transmission cables

  • Step-down transformers, near consumers, decrease the potential difference (and increase the current) to a much lower value for domestic use

The National Grid

Benefits of the National Grid

• The National Grid system is an efficient way to transfer energy due to the use of step-up and step-down transformers

• Power stations are far from most consumers, so electrical power is transmitted through a network of cables that travel across the country

• When electricity is transmitted over large distances, the resistance in the wires causes heating, which results in wasted energy transfers

• By increasing the potential difference at which the current is transmitted, the same amount of power can be transferred using a much smaller current (due to the equation P = IV)

  • This results in less heating in the wire and hence less wasted energy

• Therefore:

  • High potential difference means low current (less energy dissipated) for the same power

  • Low potential difference means high current (more energy dissipated) for the same power

• The potential difference is increased using the step-up transformers and decreased using the step-down transformers