Science at key stage 3 (Year 8)
Unit 8J: Magnets and electromagnets
Section 12: How can we explain how electromagnets work?
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Objectives |
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- that wires carrying an electric current produce a magnetic field
- that the current in a coil produces a magnetic field pattern similar to that of a bar magnet
- that the strength of an electromagnet is increased by the presence of an iron core
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Activities |
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Outcomes |
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Children: |
- Use an OHP and/or compass to demonstrate that an electromagnet has a magnetic field pattern similar to permanent bar magnets. Ask pupils to predict whether there is still a magnetic field when the iron core (the only magnetic material present) is withdrawn. Demonstrate and ask pupils to use their knowledge of magnetic materials to explain why the electromagnet's strength is far weaker without the core than with the core present. Relate this to pupils' findings in their investigation.
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- draw the field pattern of an electromagnet made from a straight coil
- explain the effect of an iron core, using ideas of magnetising materials
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Points to note |
- This work links to unit 9I 'Energy and electricity'.
- Extension: pupils could predict what the effect of straightening out the wire would be, then demonstrate the circular field pattern along the length of the wire using a perspex platform, above an OHP, on which to show the field.
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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