Electromagnetic Induction
4 marks · EasyElectricity generated at a power station is transmitted long distances before entering homes.
Explain why a step-up transformer is used before electricity is transmitted through the National Grid.
A step-up transformer increases the voltage from 10,000 V to 100,000 V. If the current in the primary coil is 50 A, and the transformer is 100% efficient, calculate the current in the secondary coil.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) To reduce energy loss in transmission wires by decreasing current and increasing voltage.
(b) 5 A
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Marking points
B1 (a) · 1 mark · Mentions reducing current.
B2 (a) · 1 mark · Mentions less energy lost as heat in wires.
M1 (b) · 1 mark · Uses correctly.
A1 (b) · 1 mark · Correct secondary coil current calculated (5 A). Allow 4.8–5.2 A.
Worked solution
a) Step-up transformers are used to increase voltage and decrease current before transmission. Lower current means less energy lost as heat in the wires, making transmission more efficient.
b) Using , with :