physics/Chem final prep (2 Viewers)

[weirdguy99]

Umm I went to USyd as well and it was explained using faradays law and lenz's law.... Also, you said that if you put a magnet on the superconductor and then cooled it, it would begin to float. This is absolutely wrong, we were shown the exact opposite, with a magnet on top of a superconductor cooled and the magnet did not budge.

http://www.youtube.com/watch?v=indyz6O-Xyw&feature=related

What's that you say?

 

[NubMuncher]

http://www.youtube.com/watch?v=indyz6O-Xyw&feature=related

What's that you say?

Touche. Rep for you, however we were shown a similar thing and the magnet did not move.

 

[weirdguy99]

Touche. Rep for you, however we were shown a similar thing and the magnet did not move.

Maybe the superconductor wasn't at its Tc.

Was this at 'Kickstart Physics'?

 

[NubMuncher]

Maybe the superconductor wasn't at it's Tc.

Was this at 'Kickstart Physics'?

Yeah lol maybe the person we got was just a total dumbass .....

 

[NubMuncher]

http://www.youtube.com/watch?v=6ATppRa7aIc

conclusive evidence. this just fucked me so hard what do we talk about in the exam :S

 

[HyperComplexxx]

http://www.youtube.com/watch?v=6ATppRa7aIc

conclusive evidence. this just fucked me so hard what do we talk about in the exam :S

Someone explain the physics behind this
Is it because of the meissner effect, the mfield of magnet cannot penetrate the superconductor thus causing it to repel?
But since it causes it to move up, surface of conductor experiences a change in flux and eddy currents are induced on surface of the superconductor such that it opposes the upward movement of the magnet(due to Lenz's law) by making a mfield to direct it back down
thus the magnet should not be levitating?
O_O wut

 

[NubMuncher]

Someone explain the physics behind this
Is it because of the meissner effect, the mfield of magnet cannot penetrate the superconductor thus causing it to repel?
But since it causes it to move up, surface of conductor experiences a change in flux and eddy currents are induced on surface of the superconductor such that it opposes the upward movement of the magnet(due to Lenz's law) by making a mfield to direct it back down
thus the magnet should not be levitating?
O_O wut

Mindfuck.

 

[weirdguy99]

Someone explain the physics behind this

A superconductor below its Tc tries to prevent its internal magnetic flux from changing. So a magnetic field from a permanent magnet is excluded because a current is induced in the superconductor. This creates a force that holds the magnet in position. The magnet does not slide off the superconductor due to quantum pinning, or something like that.

Think about it this way: if you had a magnet that began to levitate from the surface of a superconductor that has transitioned to below its Tc, there would be a change in magnetic flux. Thus, the superconductor should have a current induced that pulls that magnet back towards itself, and the levitation would not happen. That's why Lenz's Law is a weak argument.