Why does the National Grid use high voltage?
The National Grid transmits electricity at very high voltage to reduce energy wasted as heat in the cables.
GCSE Physics
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
In more detail
For a given power, increasing the voltage means the current can be much smaller (since power = voltage × current). Energy lost as heat in the transmission cables depends on the current squared (power lost = I²R), so a smaller current dramatically reduces the losses. Step-up transformers raise the voltage for efficient transmission, and step-down transformers lower it again to a safe level before it reaches homes.
Key points for the exam
- High voltage → low current → less heat lost (P_loss = I²R).
- Step-up transformer at the power station; step-down transformer near consumers.
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