A student wants to magnetise a steel rod and a soft iron rod using the stroking method. After stroking both rods with a bar magnet and then removing the bar magnet, describe what happens to the magnetism of each rod and explain why the two rods behave differently.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The steel rod becomes a permanent magnet – it keeps its magnetism after the bar magnet is removed.
The soft‑iron rod becomes only a temporary magnet – it loses its magnetism quickly once the bar magnet is removed.
Steel is a hard magnetic material; its magnetic domains are difficult to reorient but are also difficult to demagnetise, so the alignment remains.
Soft iron is a soft magnetic material; its domains are easily aligned by the external field but also easily randomised when the field is removed, so the magnetism disappears.
The soft‑iron rod becomes only a temporary magnet – it loses its magnetism quickly once the bar magnet is removed.
Steel is a hard magnetic material; its magnetic domains are difficult to reorient but are also difficult to demagnetise, so the alignment remains.
Soft iron is a soft magnetic material; its domains are easily aligned by the external field but also easily randomised when the field is removed, so the magnetism disappears.
Examiner tips
- Use the terms ‘permanent magnet’ and ‘temporary (induced) magnet’. Explain the difference in domain behaviour – hard vs soft magnetic materials. Show the cause (alignment of domains) and effect (retention or loss of magnetism).
Common mistakes
- Confusing the behaviour of steel and soft iron. Using vague phrases like ‘magnetises’ without specifying permanent or temporary. Ignoring the role of magnetic domains and material hardness/softness.
Mark scheme (4 marks)
- The steel rod retains / keeps its magnetism (becomes a permanent magnet) after the bar magnet is removed.
- The soft iron rod loses its magnetism (quickly) once the bar magnet is removed / becomes a temporary (induced) magnet only.
- Steel is a hard magnetic material so it is difficult to magnetise but also difficult to demagnetise / it retains its magnetic domains once aligned.
- Soft iron is a soft magnetic material so it magnetises easily but also loses its magnetism easily when the external magnetic field is removed.
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Describe and explain" question →
- Decode the mark scheme abbreviations →
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