This experiment investigates the magnetic field (F) along the axis of a bar magnet, based on the assumption of the inverse square law of magnetism. The magnetic field at a point along the axis of the magnet, with a dipole moment M and length 2L, is given by the formula:

Where d is the distance between the point and the center of the magnet. So

If the inverse square law is correct, therefore, the graph of  against  should be a straight line.

Significance
Understanding magnetic moment is essential in designing electromagnets, motors, and generators.