Describe how magnetic field lines are used to represent the magnetic field around a bar magnet. Include reference to what the lines show about the strength and direction of the field.

AQA GCSE Physics (8463) — 4.7.1 Permanent and induced magnetism, magnetic forces and fields · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Field lines are drawn from the north pole to the south pole outside the magnet. The direction of each line shows the direction a north pole would be pushed if placed there. Where the lines are close together the field is strong; where they spread out the field is weaker. Thus the density of lines indicates field strength and the lines themselves give the field direction.

Examiner tips

  • Use the phrase ‘drawn from north to south’ to show understanding of direction.
  • Mention that line density represents field strength.
  • Explain that lines spread out with distance to show decreasing strength.
  • Keep the answer concise – 4 points can be covered in 3–4 short sentences.

Common mistakes

  • Confusing the direction of the field with the direction of the force on a south pole.
  • Saying lines start at the south pole instead of the north pole.
  • Failing to mention that line density indicates strength.

Mark scheme (4 marks)

  1. Field lines point from north pole to south pole (outside the magnet)
  2. The direction of a field line shows the direction of the force that would act on a north pole placed at that point
  3. Where field lines are closer together the field is stronger
  4. The field strength decreases with distance from the magnet (field lines become more spread out further away)

Key terms in this question

magnetic field lines · magnetic field

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