AQA GCSE Physics

Revision Notes

2.3.5 The National Grid

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 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

power-lines, IGCSE & GCSE Physics revision notes

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
  • The current of the electricity generated from power stations is a lot more than what is required for homes and other buildings, and they must be transmitted through a network of wires that travel across the country
  • When electricity is transmitted over large distances, the current in the wires heats them, resulting in energy loss
  • By increasing the potential difference at which the electricity is transmitted, the same amount of power can be transmitted using a much smaller current (due to the equation P = IV)
    • This results in less heat being produced in the wire and hence less energy loss
  • Therefore:
    • High potential difference means low current (less energy loss) for the same power
    • Low potential difference means high current (more energy loss) for the same power
  • The potential difference is increased using the step-up transformers and decreased using the step-down transformers

Worked Example

The diagram shows part of the National Grid.

power-lines, IGCSE & GCSE Physics revision notes

Explain how the step-up transformer increases the efficiency of the National Grid.

    • In this scenario:

The useful energy is the electrical energy

The wasted energy is the thermal energy

    • The lower the current, the cooler the wire will be
    • From the diagram, the step-up transformer increases the voltage and decreases the current in the power cables
    • By decreasing the current of the transmitted electricity, the thermal energy lost through the power cables is reduced
    • Therefore, there is more electrical energy to be supplied to the homes which increases the efficiency of the National Grid

Power Loss National Grid, downloadable AS & A Level Physics revision notes

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