Physics › Section P · Magnetism › Topic P.1

Magnets, electromagnets, and field lines

A compass needle swings round without anything touching it, and a crane lifts a scrapped car with nothing but a coil of wire and a current. This topic shows where magnetism comes from, how materials respond to it, and how field lines picture it.

In this topic

  • A force without contact
  • North and south poles
  • Earth is a magnet
  • Ferromagnets and domains
  • Worked example: is it a magnet?
  • Electromagnets
  • Currents and spin: the sources of magnetism
  • Magnetic field lines
  • How strong are magnetic fields?
  • Worked example: an MRI field and Earth's field
  • Common mistakes to avoid
  • Key takeaways

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