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I have 2 magnets. I need to know the force between them. In a previous Phys.SE question, conclusion was: we need to use a dipole-dipole interaction equation, which included m, which the magnetic dipole. I searched how to calculate it, and this is what I found: m=pl where p is magnetic pole strength and l is length of the magnet. I searched a lot on how to calculate p and found nothing.

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Given the amount of emphasis we put on the electrostatic force in introductory courses I am always a bit amused by how studiously we avoid this problem. I don't think I've even seen it treated. That said, I am pretty sure that one would have to measure rather than calculate this value for any given physical example magnet. Once could then compute forces involving two of them to his or her hearts content. –  dmckee Oct 25 '13 at 1:14
    
Hint; a tightly wound solenoid with a metered current flowing through it should provide a pole of known strength. –  dmckee Oct 25 '13 at 1:51
    
@dmckee I have an idea , I already know the B of the magnet , if we have a solenoid with given turns and radius , we can easily calculate the current needed to give us B , then if there's a formula relating current to pole strength we can use and find out about. So , how to know the pole strength when current flow in a solenoid? –  user28324 Oct 25 '13 at 7:04

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