Transformers

This lesson covers transformers — devices that change the voltage of an AC supply — as required by the Edexcel GCSE Physics specification (1PH0), Topic 8: Magnetism and Electromagnetism. You need to understand the structure and types of transformers, the transformer equation, power conservation (Higher tier), and the role of transformers in the National Grid.

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What Is a Transformer?

A transformer is a device that changes the voltage of an alternating current (AC) supply. Transformers only work with AC — they do not work with direct current (DC).

Structure of a Transformer

A transformer consists of three main parts:

Component	Description
Primary coil	The input coil — connected to the AC supply
Secondary coil	The output coil — connected to the device being powered
Iron core	A soft iron core that links the two coils; it transfers the changing magnetic field from the primary to the secondary coil

graph LR
    A["AC Supply"] --> B["Primary Coil<br/>(Np turns)"]
    B --> C["Soft Iron Core<br/>(transfers magnetic field)"]
    C --> D["Secondary Coil<br/>(Ns turns)"]
    D --> E["Output Voltage"]