Re:LK-99 is an online sensation – but replication efforts fa...
by lordnacho on Friday August 04, 2023 @01:07PM
(#37002779)
Yes but why does expelling the magnetic field make it hover stably instead of just falling out of the side of the field it's in?
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Re:LK-99 is an online sensation – but replication efforts fa...
by zrezzed on Friday August 04, 2023 @01:40PM
(#37003252)
Afaik, your intuition is basically right! A superconductor exhibiting only the Meissner effect won't hover ("pin").
It's a defect (where small amounts of the field aren't expelled) that allows for the pinning to happen: https://en.wikipedia.org/wiki/Type-II_superconductor#Flux_pi...
Re:LK-99 is an online sensation – but replication efforts fa...
by space_fountain on Friday August 04, 2023 @01:29PM
(#37003118)
I think that for true hovering demos the trick is to cool the super conductor to below its critical point while it’s already inside the magnetic field. Then any way you move it will immediately induce a reacting current in the superconductor that will move it back into place. Exactly the same place since it’s a super conductor and has 0 resistance. I think in these demos though it is the fact that one side is heavier and dragging that’s leading it to stay in place
Re:LK-99 is an online sensation – but replication efforts fa...
by robinduckett on Friday August 04, 2023 @01:20PM
(#37002958)
My laymen’s interpretation is that superconductors perfectly expel the magnetic field without distorting the field and so can sit in a position that is effectively locked and held in position. I could be completely wrong however.
Re:LK-99 is an online sensation – but replication efforts fa...
by bhattid on Friday August 04, 2023 @01:41PM
(#37003262)
There's a noticeable distortion of the magnetic field near the superconductor. It's this distortion that keeps the superconductor stable - it's caused currents that appear on the surface which match and cancel* the surrounding field.
*some of the magnetic field penetrates onto the surface of the superconductor, but internally, there's 0 magnetic field within the superconductor.
Re:LK-99 is an online sensation – but replication efforts fa...
by bhattid on Friday August 04, 2023 @01:48PM
(#37003357)
When a superconductor interacts with a magnetic field, currents generate at the surface of the superconductor that will produce their own magnetic field, which cancels the external one. The superconductor doesn't fall out to the sides because the field gets cancelled and there's no net force acting on the conductor.
There can still be torque (i.e. rotations) for type I superconductors, and type II superconductors when they're fully superconducting. I'm not familiar with how the specific dynamics work though - I'm guessing it's related to gravity?