# Magnetic moment between 2 bar magnets

#### JGBuck94

1. The problem statement, all variables and given/known data
A bar magnet floats above another bar magnet. The first has mass u1 and magnetic moment m1=m1k^ and is on the ground. The second has mass u2 and mag. moment m2=-m2k^ and is a distance z above the ground, find z

2. Relevant equations

I assume I need to calculate the magnetic force between the 2 and equate that to the gravitational force, so;
Bdip(r)=(u0/4pi*r3){3(m.r^)r^-m}
and FB=IBw
and Fg=-u2g

3. The attempt at a solution
I'm not entirely sure how to begin this question, I think I need to balance out the gravitational force and magnetic force to find the equilibrium position of the floating bar magnet and the magnetic moments will superpose because of the uniform magnetic field, my main problem is using that equation for the magnetic field, I haven't seen it before and I am just going by Griffiths which seems to imply this equation will only work with a circular loop (?)

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Gold Member

#### BiGyElLoWhAt

Gold Member
So, I think the I is from the electron orbits, and it'd be a sum of all of them. I think that's taking it too far. You have the moments, and you have the mass, and you know g. Just balance the forces or use energy or whatever (I guess you'll still end up using forces, ultimately).

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