I recently learned that the strength of a Magnetic field around a conductor is p
ID: 1375611 • Letter: I
Question
I recently learned that the strength of a Magnetic field around a conductor is proportional to the current flowing in it. So if we have a Mercury wire at absolute zero and pass a current through it (Resistance = 0) and then toss some iron filings at it, will the filings cylindrically float around the conductor (along the Magnetic field lines) due to the extreme strength of the field or just behave the way they do for an ordinary conductor (like Copper), in which case we must rest the filings on cardboard and then give it a jerk to align it along the lines.
Explanation / Answer
First thing: even with huge fields, iron will not "float" like that in circular motion. Iron will always be attracted to the region where the magnetic field is the most intense: which is in contact with the conductor/superconductor.
In addition, there is a limit to the magnetic field you can achieve with any superconductor: it is called the critical field. There are 2 types of critical fields, Hc_1 and Hc_2, which correspond to 2 things:
Hc_1 corresponds to the maximum field that can be "ejected" (screened) automatically by the superconductor (Meissner effect: en.wikipedia.org/wiki/Meissner_effect). It corresponds to a magnetic energy (B^2/(2*