Mammoth Memory

Proving which way magnetic lines on a magnet travel

If you sprinkle iron filings around a magnet, the small iron filings react to the magnetic forces and position themselves along the magnetic lines.

Iron filings sprinkled around a magnet.

To find which direction the magnetic lines travel, take a small compass and place it near one pole of the magnet and mark the positions of the ends N and S of the compass needle with pencil dots. Then move the compass so that the S end of the compass needle is over the dot you previously placed at the N end and mark the new position of the N end with a third dot. Keep repeating this until you reach the other end of the magnet.

Magnetic lines going north to south.


Dots showing magnetic field

We can now join the dots up.

Joined up dots showing magnetic field

This shows a field line of the magnetic field.

Magnetic field lines of a bar magnet

If we keep plotting the field lines around the magnet in different positions you should get the magnetic field plot above.

Magnetic field lines of a horse shoe magnet

If you plot the field lines around a horseshoe magnet you should get the magnetic field plot above.

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