A permanent magnet produces its own magnetic field. An induced magnet is a…

The idea

A permanent magnet, such as a bar magnet or a horseshoe magnet, produces its own magnetic field all the time, so it attracts magnetic materials and interacts with other magnets even when nothing else is nearby. An induced magnet behaves differently: a magnetic material such as iron or steel becomes a magnet only while it is inside a magnetic field. The field aligns the magnetic regions inside the material, so the material gains poles and is attracted to the magnet producing the field. Induced magnetism always produces attraction, never repulsion, because the near pole of the induced magnet is always unlike the pole of the permanent magnet facing it. Once the material is removed from the field, it loses most or all of its magnetism quickly, which is why a paper clip picked up by a magnet does not stay strongly magnetic for long.

What earns the marks

• State that a permanent magnet produces its own magnetic field continuously, without needing another magnet nearby.
• Define an induced magnet as a magnetic material that becomes a magnet when placed in a magnetic field.
• Explain that induced magnetism always causes attraction, because the induced pole facing the permanent magnet is always unlike it.
• Describe that an induced magnet loses most or all of its magnetism quickly when removed from the magnetic field.
• Distinguish between permanent magnets and induced magnets using examples, such as a steel bar magnet compared with an iron nail temporarily magnetised by a magnet.

Common mistakes and how to put them right

• Thinking that an induced magnet can repel a permanent magnet.

  Put it right: Induced magnetism always causes attraction, because the induced near pole is unlike the permanent magnet's facing pole.

• Believing that an induced magnet keeps its magnetism permanently after removal from the field.

  Put it right: It loses most or all of its magnetism quickly once the field is removed.

• Confusing a permanent magnet with an induced magnet by saying both produce their own magnetic field.

  Put it right: Only a permanent magnet produces its own field; an induced magnet becomes magnetic only in an external field.

Exam tips

• Use the phrase 'induced magnet' accurately and link it to a magnetic material placed in a magnetic field, rather than calling every magnetic object a permanent magnet.
• When explaining attraction between a magnet and an unmagnetised iron object, state that the iron becomes an induced magnet and is therefore attracted.
• Contrast permanent and induced magnets in a table or sentence pair to make the difference in field production and retention of magnetism clear.