The National Grid (OCR Gateway 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 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 heating 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