An electromagnet is used in a scrapyard to lift pieces of scrap iron. Explain why an electromagnet is more suitable for this purpose than a permanent magnet.

Cambridge International IGCSE Physics (0625) — 4.5 Electromagnetic effects · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

An electromagnet can be switched on and off by controlling the electric current, so the scrap iron can be released when the current is turned off.
A permanent magnet always produces a magnetic field and cannot be switched off.
The electromagnet’s field strength can be increased or decreased by changing the current, allowing the operator to lift heavier or lighter pieces of scrap.

Examiner tips

  • Use the word ‘switch on/off’ to show control of the field. Mention that the field can be varied by changing the current. Show the contrast with a permanent magnet’s constant field.

Common mistakes

  • Failing to state that the electromagnet can be switched off. Confusing the ability to vary strength with a permanent magnet. Using vague terms like ‘stronger’ without linking to current.

Mark scheme (4 marks)

  1. An electromagnet can be switched on and off (by switching the current on and off)
  2. This allows the iron/scrap metal to be released/dropped when the current is switched off
  3. A permanent magnet cannot be switched off / always produces a magnetic field
  4. The strength of the electromagnet can be varied by changing the current

Key terms in this question

electromagnet · permanent magnet

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