The Magnetometer

Adapted from a TOPS Terra Bagga activity

Magnetic fields are invisible; we can only see the effects of the magnetic force.
Magnetometers are devices used to detect and measure the strength of magnetic fields. Compasses are basically magnetometers with directions marked on them. A magnetometer will dip or point toward a source of magnetism.


What are the 'big ideas' I want my students to grasp?
  • The Earth has magnetic poles.
  • Magnetic poles move.
  • Magnetic reversals can be observed on either side of the mid-oceanic ridges.
  • Magnetism is a measure of a planets' internal conditions: the core, convection, etc.
  • Objective

    What do I want my students to know and be able to do?
  • Build an instrument they use to find the polarity of an object
  • Find the magnetic poles on a model (Earth, Mars, Io, Ganymede, etc.)
  • Explore a model of magnetic reversals.
  • Purpose

    To build an instrument capable of detecting a magnetic field, or be able to locate magnetic poles.

    Materials (Per person)

    4-inch piece of plastic straw
    2 straight pins
    masking tape
    sewing thread


    1. Use a small piece of masking tape to hang two straight pins from a piece of thread. The pins should point in opposite directions and hang horizontally.

    2. Push the thread through the straw. Tape the thread to the top so that the pins have just enough clearance to swing freely at the bottom.

    3. Stroke the pins from left to right several times with a permanent magnet.

    4. Establish and mark the north-seeking end.

    Last modified prior to September, 2000 by the Windows Team

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