What 'magnetic dipoles' ? You can use F=B*I*l (Laplace magnetic force)
where B/H=Mu for isotropic media (i.e. air coils and no armature).
H=I/(2*PI*d) at a distance d from an infinitely long wire carrying a
current I, and H=2*I/r in the center of a single turn coil of radius r,
H=N*I/l inside a long and narrow solenoid (the last formula is empirical
afaik - the exact version is very hairy). If the coil(s) have cores with
Mu different from air then B will be non-linear and probably change with
the inverse square of the distance if the distance between the poles is
reasonably large (larger than the diameter of the pole pieces) so
alignment errors do not play a major role. So F ~= N*I*B/(l*r*d^2) for d
>= 2r where B is the induction from a nearby magnet or other coil. Try a
book near you ?

If you have trouble with the maths you can use a scale with a nonmagnetic
table to get real life values for coils you make or obtain and magnets you
own (remember F=BIl, and F is proportional to Ampere-turns). You can even
calibrate your coils using a compass needle to get a fairly accurate
(+/-10%)  reading on B at some distance from the magnets/coils (earth
field ~= 45uT +/-5uT but not horizontal in most places, and NOT inside or
near armored concrete buildings).

Peter

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