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Find the Power!

In this activity, students use paper clips to find the parts of a magnet where the magnetic field is concentrated.

Magnetic field lines don’t exist physically — they’re a mathematical construct to help us visualise how magnets work. However, iron filings around a magnet will line themselves up along the field lines, so we can then see how the magnetic field “looks”.

Conventionally, we say that magnetic field lines leave the north end (pole) of a magnet and enter the south end (pole) of a magnet. The forces of a magnet are strongest at the poles. This is because the magnetic field tends to be concentrated at the poles (and spread out and bulging between them).

Objectives

  • Explain the concept of a magnetic field.

Materials

  • Per Student or Group:
    bar magnet
    small paper clips
    string
    tape
    cardboard

Key Questions

  • What parts of the magnet are the most attractive?

What To Do

  1. Using string and tape, hang the magnet from a doorframe or table (the magnet should be level).
  2. Spread all of the paper clips on a piece of cardboard. You can draw around the paperclips so you know where they started.
  3. Raise the flat surface with the paper clips toward the magnet (until almost touching the magnet). Be careful to raise the surface as gently as possible so the paper clips don’t move unless they’re attracted to the magnet.
  4. Lower the cardboard and examine where the paperclips stick to the magnet.

Extensions

  • Map out the magnetic field using iron filings. What is the relationship between the field lines and the highly attractive poles?