A student places a plotting compass near a bar magnet. Explain what happens to the compass needle and why, as the student moves the compass from a position far away from the magnet to a position close to one of its poles.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A bar magnet has a north pole at one end and a south pole at the other. A small plotting compass contains a magnetised needle that can rotate freely.
Model answer (4 marks)
The compass needle is deflected and aligns with the magnetic field produced by the bar magnet.
As the student moves the compass closer to a pole, the magnetic field strength increases.
The needle therefore rotates more strongly and points along the field lines, becoming more pronounced nearer the pole.
As the student moves the compass closer to a pole, the magnetic field strength increases.
The needle therefore rotates more strongly and points along the field lines, becoming more pronounced nearer the pole.
Examiner tips
- Use the word ‘deflected’ or ‘aligns’ to show the action of the needle.
- Mention the magnetic field of the bar magnet and that the needle follows it.
- Explain that the field strength is greater nearer the pole, giving a stronger deflection.
- Keep the answer concise – 4 marks can be earned with 2–3 short sentences.
Common mistakes
- Failing to mention the magnetic field or the needle aligning with it.
- Using vague terms like ‘moves’ instead of ‘deflects’ or ‘aligns’.
- Not recognising that the deflection increases as the compass approaches the pole.
Mark scheme (4 marks)
- The compass needle is deflected / rotates / aligns when near the magnet
- The bar magnet produces a magnetic field around it
- The compass needle lines up along / points in the direction of the magnetic field at that position
- The closer the compass is to the pole, the stronger the magnetic field, so the deflection / alignment is more pronounced / happens more strongly
Key terms in this question
Related
- All WJEC GCSE Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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