# About magnetized spheres

1. Oct 11, 2008

### geneen

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.

Last edited by a moderator: Oct 13, 2008
2. Oct 12, 2008

### granpa

you mean uniform magnetization throughout?

the distance between them is 2r

3. Oct 12, 2008

### geneen

Hi

the question is exactly like that

( A permanent magnet alloy of samarium and cobalt has a magnetization M= 7.5*10^5 J/T.m^3 . Consider two magnetized spheres of this alloy each 1 cm in radius and magnetically stuck together with unlike poles touching. What force must be applied to separate them??)

Note: before I post my question I tried the distance 2r but still i can't find the right result !! what is the formula??

thanks.

4. Oct 13, 2008

### geneen

isn't here suitable for this kind of questions ? or I must put it in another branch?

thanks

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