two short magnets apply a force F on each other, if the separation between them is halved then what's the new force between them approximately?

ans.. 16F

A bar magnet can be considered as a magnetic dipole. Now the force between two magnetic dipole is given by
F=3μ02πm1m2r4
Where r is the distance between them. Now if the distance is halved the new force will be
Fnew=3μ02πm1m2r24=163μ02πm1m2r4=16F
So new force will be 16 times of the old force.

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