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 When a current flows in a wire a magnetic field is around the wire.
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An electromagnet is a coil of wire (usually with a core in it - but the core is NOT the electromagnet the coil is the important bit!). When a current passes through the coil it acts like a magnet - when no current flows there is no magnetic field.
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The bigger the current, the stronger the field,
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The greater the number of turns, the stronger the field
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The stronger the field the closer the field lines - they are more densely packed.
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The presence of a soft iron core increases the strength of the field substantially but the core must be soft iron otherwise when the current is switched off the core would still be magnetised.
- Electromagnets are used in domestic and industrial devices, eg electric bells, lifting magnets, relays
- Wires carrying an electric current produce a magnetic field with concentric circular field lines around them.
- The current in a coil produces a magnetic field pattern similar to that of
a bar magnet
- The strength of an electromagnet is increased by the presence of an iron core
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