1. The problem statement, all variables and given/known data This is a past exam question which I just for the life of me can't figure out. http://tinypic.com/r/2eq6ryo/8 2. Relevant equations My guess is that the energy of the magnetisation is equal to the gravitational energy Relevant Equations: Ems = Mass * g * δ Where Mass = ρ * ACross Section * π * r (not 2πr as we are only using half the loop, also cross sectional r is negligible.) 3. The attempt at a solution I don't know what the energy of magnetisation is, and definitely don't know how to get to it via the current. Any relevant equations would be much appreciated.