TRANSFORMERS AND NATIONAL GRIDS
2 marks · EasyExplain why it is important to use high voltages when transmitting electricity over long distances in the National Grid.
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Using high voltages in transmission reduces the current in transmission lines, which reduces energy lost as heat. This makes power transmission more efficient.
Also accept: High voltage means smaller current so less heat is lost, making transmission more efficient
Common mistakes: High voltage increases energy loss; Low voltage is safer for long distances
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Marking points
B1 · 1 mark · Identifies that high voltage leads to low current in the wires.
B2 · 1 mark · States that low current reduces energy loss as heat/less energy is wasted.
Worked solution
When electricity is transmitted at high voltage, the current in the transmission wires is smaller. Because energy lost as heat depends on the current squared, lowering the current means less energy is lost. This makes transmission more efficient.