ELECTROMAGNETISM
4 marks · NormalA student places a steel nail and an iron nail near a bar magnet and observes what happens.
Explain what is meant by 'induced magnetism' in this context.
Both nails become attracted to the magnet, but only one remains magnetised after removing the magnet. Which one, and why?
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Show answer
(a) Induced magnetism is when a material becomes magnetic because it is placed within a magnetic field. · must show Definition refers to gaining magnetism from a field, Temporary nature mentioned
(b) The steel nail remains magnetised because steel is magnetically hard. Iron is magnetically soft so loses its magnetism when the magnet is removed. · must show Steel is hard and retains magnetism, Iron is soft and loses magnetism
Common mistakes: Confusing temporary and permanent magnetism; Mixing up properties of iron and steel
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly states what induced magnetism is.
A1 (a) · 1 mark · Mentions it happens in a magnetic field, and the effect is temporary.
B1 (b) · 1 mark · Correctly identifies that steel remains magnetised.
B2 (b) · 1 mark · Explains why based on magnetic hardness/softness of materials.
Worked solution
(a) Induced magnetism means that a material becomes magnetic only while it is in a magnetic field. The field from the bar magnet causes the nails to become temporary magnets.
(b) The steel nail is magnetically hard so it keeps some magnetism after removing the magnet, while the iron nail, which is magnetically soft, loses all magnetism when the magnet is removed.