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.
To find which direction the magnetic lines travel, take a small compass and place the compass 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 until the end of the compass is over the second dot and mark the new position of the other with a third dot. Repeat this as many times as you can until you reach the other pole.
We can now join the dots up.
This shows a field line of the magnetic field.
If we keep plotting the field line around the magnet you should get the magnetic field plot above.
If you plot the field lines around a horseshoe magnet you should get the magnetic field plot above.