English: A bar magnet resting on a compass board, an educational tool to display the shape of its magnetic field, showing how magnetic field lines are drawn. The board is covered with an array of magnetic "compasses", each consisting of a magnetized steel needle in a plastic bubble which can turn freely. The compass needles turn until they are parallel to the magnetic field of the magnet at each point. It can be seen that the magnet has two locations called poles at either end at which the field is concentrated. By drawing lines which follow the direction of the compass needles (B, blue), a field line diagram can be constructed. It shows the magnetic field emerges from the north pole of the magnet (N) at left, curves through space to the other end of the magnet, and enters through the south pole of the magnet at right.