GCSE Physics

Transforming Voltage

So if the secondary coil experiences a changing magnetic field, an alternating voltage VS will be induced across it! The size of this voltage changes depending on the number of turns of wire in each coil:

transformer showing primary and secondary coils, laminated iron core and primary and secondary voltages

In the diagram above, the primary coil has more turns than the secondary. This means that the changing magnetism has less effect on the secondary coil and a lower voltage is produced. This is a step-down transformer because the voltage goes down.

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