The superconductivity group at the University of Tel Aviv, led by Professor GuyDeutscher, devotes part of his research time to a very commendable action: making physics of superconductors accessible to young people and adults throughthe explanation of phenomena unique as levitation / trapping quantum.
This demonstration distributed educational kits (available soon), formed by a diskand a kind of cycle of magnets to cause these physical effects in a didactic and certainly intuitive, as seen in this video.
Some models of magnetic levitation train, or maglev, use this physics, enabling them to levitate move at high speeds, limited only by air resistance to its progress.
In this case the train is converted into a disk, a sapphire crystal wafer covered witha thin (~ 1um thick) of a ceramic material composed of oxides of yttrium, bariumand copper (YBa 2 Cu 3 O 7-x .) This ceramic layer has no electrical or magnetic properties at room temperature interesting.
However, when the disc is cooled below -185 ° C with liquid nitrogen (not suppliedin the kit, as the protective kitchen plastic) material is converted into asuperconductor, conducting electricity without resistance, without energy loss.
And here are the magnets in the game. Superconductivity and magnetic fields do not get anything right. When possible, the superconductor expel all magnetic field lines from the inside. This is the Meissner effect governing the magnetic levitation.
In this case, because the superconductor is extremely thin, the magnetic field does not penetrate. However, it does, in discrete amounts (this is quantum physics, after all) are those called flux tubes.
Within each magnetic flux tube is locally destroyed the superconductivity. So that the superconductor is maintained magnetic tubes "caught" in the weak zones (eg,in the grain boundaries).
Any spatial movement of the superconductor will cause the flow tubes move with itas if tensioners, the superconductor being "trapped" in the air, so that the distancemaintained without friction with the body generated by the field, even maintaining agiven position. It is the phenomenon of "quantum catch" and it seems like magic.
But it's not magic. It's just physics. And this teacher explains it masterfully.
