IGCSE Physics / Electric motors and electromagnetic induction
Transformers
Edexcel International GCSE Physics (4PH1), chapter 21: Electric motors and electromagnetic induction, specification point 6.17P. Part of the full course.
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A transformer uses a changing magnetic field to transfer energy between two coils and change an alternating voltage. The number of turns on the secondary coil determines whether the output voltage is higher or lower.