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GCSE Physics · AQA 8463 · Topic 4.7

Magnetism and electromagnetism

Key points

  • Like magnetic poles repel and unlike poles attract. A magnetic field is the region where a magnet or magnetic material feels a force.
  • Permanent magnets make their own field; induced magnets only become magnetic inside a field. Iron, steel, cobalt and nickel are magnetic materials.
  • A current in a wire produces a magnetic field around it. A solenoid with an iron core makes an electromagnet.
  • The motor effect: a current-carrying wire in a magnetic field feels a force, F=BIlF = BIl. Fleming's left-hand rule gives the direction.
  • (Separate physics) Moving a wire in a field, or changing the field through a coil, induces a potential difference. This is used in generators, microphones and transformers: VpVs=npns\frac{V_p}{V_s} = \frac{n_p}{n_s}.

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Magnetism and electricity are closely linked: a current makes a magnetic field, a magnetic field can push on a current, and a changing magnetic field can create a potential difference. Those three ideas run motors, loudspeakers, generators…

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Sub-topics

  1. 4.7.1Permanent and induced magnetism, magnetic forces and fields
  2. 4.7.2The motor effect
  3. 4.7.3Induced potential, transformers and the National Grid

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