The National Grid (AQA GCSE Physics: Combined Science)

• 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 which increase the voltage (and reduces the current) through the wires
  • Step-down transformers which decrease the voltage (and increases the current) through the wires

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
• The current generated by power stations is greater than that which is required for homes and other buildings, and so it must be transmitted through a network of wires 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

• • The lower the current, the less heating due to resistance there will be in the wires 
  • From the diagram, the step-up transformer increases the voltage and decreases the current in the cables
  • By decreasing the current, the energy dissipated to the thermal store of the surroundings through the power cables is reduced
  • Therefore, there is more energy being transferred to homes which increases the efficiency of the National Grid