This isn't a homework problem, but I figured I'd post it here since it's a pretty basic question, in my view at least. So my professor and Senor Griffiths have been telling me this for the past year. Cool. Now I'm working on a project that uses a superconducting magnet. So I started to think, and here's my question: If I have a superconducting magnet, i.e. a solenoid that has I guess you call it persistant current running through it at 0 Ohms, it will (or should) have it's magnetic field for almost infinity. Now if I introduce a wrench into the system, the B-field will attract it and bring it closer. As this happens, will the B-field lose strength because it is transferring energy to both the wrench and magnet itself as kinetic energy? If I do this very slowly so that when they touch, very minimal heat is released (so I guess the B-field is low), what would happen if I pulled them apart again? I'm guessing the magnet would not inscrease in strength once more. Am I thinking correctly?