Magnetism
4 marks · EasyIron nails are placed near a bar magnet on a sheet of paper. The teacher sprinkles iron filings around the bar magnet and taps the paper gently. Describe what pattern would be formed by the iron filings, and what this shows about the magnetic field.
State what happens to the iron nails near the magnet.
Explain why the iron filings make lines and the shape of these lines.
The teacher removes the bar magnet and the iron filings are brushed away. At the same spot, the teacher places a steel nail instead of an iron nail. What difference would you expect in how long the nail remains magnetised after the magnet is removed? Explain your answer.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a(i)) The iron nails become temporary magnets and may be attracted to the bar magnet.
(a(ii)) The iron filings form curved lines from the north to the south pole, showing magnetic field lines which reveal the field's shape and direction.
(b) The steel nail stays magnetised after the magnet is removed, as steel is magnetically hard; unlike iron which quickly loses its magnetism.
Common mistakes: Saying the field lines go from south to north; Claiming steel is magnetically soft
Show mark scheme and worked solution
Marking points
B1 (a(i)) · 1 mark · Correctly states what happens to the iron nails (become temporary magnets or are attracted).
B2 (a(ii)) · 1 mark · Correctly describes that iron filings form field line patterns from north to south pole and explains this shows shape/direction of field.
B3 (b) · 1 mark · States steel remains magnetised after removal but iron does not.
B4 (b) · 1 mark · Correctly explains this is due to steel being magnetically hard and iron being soft.
Worked solution
a(i) The iron nails, being made from a magnetic material (iron), will become temporarily magnetised and may stick to the bar magnet.
a(ii) Iron filings line up along magnetic field lines. The pattern will show curved lines leaving the north pole and entering the south pole, making the field visible.
b) The steel nail will remain magnetised after the magnet is taken away, because steel is magnetically hard (keeps magnetism). Iron quickly loses magnetism because it is magnetically soft.