Magnetic lines of force: It may be defined as the curve the tangent to which at any point give the direction of the magnetic field at that point.

Properties of lines of force:

1. Magnetic lines of force are closed curves starts from N-pole and end at the S-pole and then return to the N-pole through the interior of the magnet.
2. The lines of force never cross each other.
3. They start from and enc on the surface of the magnet normally.
4. The relative closeness of the lines of force gives a measure of the strength of the magnetic field which is maximum at the poles.