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The National MagLab is funded by the National Science Foundation and the State of Florida.

Compasses in Magnetic Fields

The invention of the magnetic compass radically changed the way humans navigated from place to place. Travelers could orient themselves even when the skies were cloudy and there wasn’t a landmark in sight.

Compasses point north because the Earth has a magnetic field. The compass needle responds to the earth’s field because it’s made from ferromagnetic material and has been magnetized. But what happens when a new magnetic field from a permanent magnet is introduced?

The tutorial below simulates how you can move the needle of a compass with a permanent magnet.


  1. Observe the direction the compass needle is pointing.
  2. Drag the permanent magnet around to see how it impacts the direction the needle points.
  3. Hide the magnet and watch the needle point north when it’s only in the earth’s magnetic field.

We associate compasses with pointing north, but the direction of arrow can be manipulated. When the permanent magnet is present, it overrides Earth’s magnetic field because it’s stronger. The closer the magnet is to the compass, the more powerful the effect.

No one knows for certain what generates Earth’s field, but one widely accepted explanation points to the currents and turbulent activity happening inside the molten iron core of the planet. The true north and south poles of the field move around and can even reverse periodically. Meaning the compasses of the past might be pointing a different direction than the compasses of the present and future.

To learn more about how compasses were invented and used in the past read up on the Early Chinese Compass.