An inductor consists of a coil of wire, usually surrounding a core of ferromagnetic material. The ferromagnetic material may be iron itself or an iron-containing material known as ferrite. An iron core is usually made from layers of sheet iron. Another kind of inductor, is the internal aerial of a portable radio set, which consists of a rod of ferrite on which is wound one or more tuning coils.

Electricity and magnetism

When a current flows through a coil of wire a magnetic field is generated. This is represented by lines of magnetic force, which show the direction in which the needle of a compass points. If there is a ferromagnetic core in the coil, the lines gather to flow through the core. The field is mainly confined to the core, ...

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