A current-carrying wire is placed between the poles of a permanent magnet so that the wire is perpendicular to the magnetic field. Explain why the wire experiences a force and describe how the direction of that force can be determined.

Edexcel GCSE Physics (1PH0) — 12.1 Magnetism and the motor effect · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

A current‑carrying wire creates a magnetic field around it.
The magnetic field of the wire interacts with the magnetic field of the permanent magnet.
The resulting force is perpendicular to both the direction of the current and the magnetic field.
Fleming’s left‑hand rule is used: thumb gives the force, first finger the field, second finger the current.

Examiner tips

  • Use the exact wording ‘perpendicular to both the current and the magnetic field’ to gain the full 4 marks.
  • Mention Fleming’s left‑hand rule and the positions of the thumb, first and second fingers.
  • Show the sequence of reasoning: current → magnetic field → interaction → force direction.
  • Keep the answer concise and avoid unnecessary detail.

Common mistakes

  • Confusing the right‑hand rule with Fleming’s left‑hand rule.
  • Failing to state that the force is perpendicular to both the current and the magnetic field.
  • Not specifying which finger represents the magnetic field and which represents the current in Fleming’s rule.

Mark scheme (4 marks)

  1. The current in the wire produces a magnetic field around the wire
  2. This magnetic field interacts with the magnetic field of the permanent magnet
  3. The force is at right angles to both the current direction and the magnetic field direction
  4. Fleming's left-hand rule is used to determine the direction of the force, using the thumb for force, first finger for field and second finger for current

Key terms in this question

magnetic field · permanent magnet · current-carrying wire

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