When removed from the magnetic field an induced magnet loses most/all of…

The idea

Take the external field away and an induced magnet loses most or all of its magnetism, and it does so quickly. Without the field to hold them, the domains fall back into a random arrangement and the poles disappear, which is why a chain of nails collapses the instant the bar magnet is lifted clear. The mark scheme allows 'when there are no magnets nearby' for removing the field. How complete the loss is depends on the material: soft iron loses essentially all of it at once, while steel is harder and keeps a good deal, which is why steel is used for permanent magnets and iron for electromagnet and transformer cores that must switch off cleanly.

What earns the marks

• Stating that an induced magnet loses most or all of its magnetism when removed from the magnetic field; 'when there are no magnets nearby' is allowed.
• Stating that the loss happens quickly.
• Stating that the domains return to a random arrangement so the poles disappear.
• Applying it, such as explaining why a chain of nails drops when the magnet is taken away.

Common mistakes and how to put them right

• Writing only that it stops being a magnet, with no reference to removing the field.

• Treating iron and steel as behaving identically once the field is removed.

• Claiming the nails stay magnetised permanently because they have touched a magnet.

• Saying the magnetism fades over hours rather than almost at once.

Exam tips

• Both 'quickly' and 'removed from the magnetic field' can earn credit, so include both.
• Use the chain of nails as the worked example for the applied mark.
• Contrast soft iron with steel if the question asks about a choice of material.