The national grid

• The national grid is a system of cables and transformers linking power stations to consumers
• Electrical power is transferred from power stations to consumers using the national grid
• • step-up transformers are used to increase the potential difference from the power station to the transmission cables
  • then step-down transformers are used to decrease the potential difference to a much lower value for domestic use
• • To transmit the huge amount of power needed, you need either a high potential difference or a high current because P=IV.
  • The problem with a high current is that you lose loads of energy as the wires heat up - it is much cheaper to boost the potential difference up really high and keep the current as low as possible - this is what the step-up transformer does.
  • This prevents heat escaping through the wires, making the National Grid very efficient.