Hi ... how can I calculate the force between two permanent magnetized spheres(each r in radius) and has a magnetization (M) when they are magnetically stuck together with unlike poles touching?? I tried to think about it and found the following: 1) I can treat it like earth magnetic field and imagine there is a bar inside the sphere. 2) because there is no distance between the spheres I must calculate the force for one sphere then multiply it by 2. 3) the formula must have the M,V, meu( permeability of free space). but I can't find such formula which give me the right result ( yes I have the answer in number, it is GRE question) thanks in advance.