A student strokes a steel knitting needle repeatedly in the same direction with one pole of a permanent magnet. Describe what happens to the knitting needle during this process and explain why the needle retains its magnetism after the permanent magnet is removed.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Stroking the needle aligns the magnetic domains in the steel so that they all point in the same direction. The needle becomes magnetised and acts as a temporary magnet. Because steel is a magnetic material, the domains remain aligned even after the external field is removed. The needle therefore retains its magnetism and behaves as a permanent magnet, producing its own magnetic field without an external source.
Examiner tips
- Use the word ‘domains’ and ‘align’ to show understanding of the process
- Explain that steel is a magnetic material that can retain domain alignment
- Mention that the needle now produces its own field
Common mistakes
- Calling the needle a permanent magnet from the start
- Forgetting to state that the domains remain aligned after the magnet is removed
- Using vague terms such as ‘magnetised’ without explaining the domain alignment
Mark scheme (4 marks)
- Stroking aligns the magnetic domains (in the steel) in the same direction
- The knitting needle becomes a (temporary/permanent) magnet / is magnetised
- Steel is a (magnetic) material that retains its magnetism / domains remain aligned after the permanent magnet is removed
- This means the needle now acts as a permanent magnet (producing its own magnetic field without needing an external field)
Key terms in this question
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Describe and Explain" question →
- Decode the mark scheme abbreviations →
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