021

021 – Magnetic Field Lines

Basic experiment for magnetic field lines

Visualization of a magnetic field (with iron powder)

Magnetic field of a bar magnet

Introduction to:

Field concept, field lines, magnetic field

Material:

  • bar magnet
  • iron powder (iron filings)
  • Glass plate / Plexiglas plate / solid cardboard with a sheet of  paper above

Construction and implementation:

  • Place the glass plate over the magnet
  • sprinkle the iron powder finely and evenly onto the glass plate from a height of 30-50 cm
  • Lightly tap against the glass plate several times

Observation:

  • The iron powder arranges itself into a pattern that shows the magnetic field lines.
  • In the vicinity of the magnet, the filings do not remain lying down, but are pulled to the poles. There they straighten up.

Explanation:

  • The iron filings are magnetized in the magnetic field and form chains of magnetic dipoles.
  • These are aligned along the field lines.

Tips:

  • Attention: Do not bring iron filings directly onto the magnet, they are very hard to remove from there.
  • Collecting the iron powder: wrap two layers of a paper towel around a magnet to collect the powder, then spread the towel flat over a jar (powder on the bottom side) and pull magnet upwards

Didactic potential:

  • The abstract term “magnetic field” is visualized.
  • Differently shaped magnets have different magnetic fields: experiments with neodymium magnets  or a horseshoe magnet are worthwhile.
  • With a powerful magnet and many iron filings, a three-dimensional field line image can also be generated.