force between two magnets

[anita1984]

Hello forum,
How to calculate the force between two magnets at each distance r ? can i use Coulomb law ?

Thanks in advance

[jrlaguna]

No, it's the force between two magnetic dipoles, see here http://en.wikipedia.org/wiki/Magnetic_moment#Forces_between_two_magnetic_dipole s

The idea about how to derive it: the magnetic field between the two magnets has a certain energy. If the two magnets come closer, the energy is reduced. Hence the force.