I observed an experiment the other day where a magnet was immersed in liquid nitrogen and placed in a petri dish.

 

Next, a small ball-bearing was placed in the petri dish just above the magnet and I was rather intrigued as it floated a few millimeters above the magnet.

 

i wanted to know the theory behind this, in other words, why does this happen? My theory so far (this is only a guess) is that liquid nitrogen distorts the magnetic field so that it pushed the ball bearing upward instead of attracting it. Is this right?

no superconductors repel magnetic fields the liquid nitrogen does nothing but keep the superconductor cool

I observed an experiment the other day where a magnet was immersed in liquid nitrogen and placed in a petri dish.

 

Next' date=' a small ball-bearing was placed in the petri dish just above the magnet and I was rather intrigued as it floated a few millimeters above the magnet.

 

i wanted to know the theory behind this, in other words, why does this happen? My theory so far (this is only a guess) is that liquid nitrogen distorts the magnetic field so that it pushed the ball bearing upward instead of attracting it. Is this right?[/quote']

 

You got the topic right! The ball is elevated by the magnetic field created by the superconductor. The superconductor only works when it's really really really cold. When it's "hot" (i.e. room temperature), the superconductor loses its superconductivity and becomes a useless piece of junk. That's where the liquid nitrogen comes in.

We had quite a long post on this not too long ago,

 

http://www.scienceforums.net/forums/showthread.php?t=9122

 

Some interesting links in there for information about it if I recall.

 

As stated above the liquid nitrogen is just for cooling, cooling a superconductor, makes it work, so you get the super conductivity...

positron said "a small ball-bearing ". I believe it was not that but a superconductor! Thus what you saw, was the meisnner effect between a superconductor and a magnet.