# 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 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. 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  ### Author: Ashika

Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
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