CAIE IGCSE Physics Temporary and Permanent Magnets

Practise comparing soft iron and steel by how readily each magnetises and retains magnetism, then select the correct material for a device or test result.

Exam points

select soft iron for an electromagnet core because it magnetises and demagnetises easily
select steel for a permanent magnet because it is harder to magnetise but retains magnetism
infer the material from pins retained after current is switched off or an armature's behaviour

[Maximum number: 2]

Fig. 7.1 shows a barrier at the entrance to a car park. The wooden barrier arm has a weight of 60 N which acts through the centre of gravity at the position shown on Fig. 7.1.

Fig. 7.1

Fig. 7.2 shows a coil attached to a power supply placed below the soft iron bar A.

Fig. 7.2

A student suggests that the soft iron bar A is replaced by a steel bar. Explain why a steel bar is less effective than a soft iron bar in the barrier.

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4.1.3—Differences between the properties of question 1