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Message: <blockquote data-quote="BRAINY" data-source="post: 1743757" data-attributes="member: 68727">here we goooooooo!!!!!!!!!!!This is called Superconducting Levitation<img src="http://www.fys.uio.no/super/levitation/looplev.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />Superconductors expel magnetic field, and hence repel magnets. This repulsion can be stronger than gravity, which leads to levitation - the most fascinating manifestation of superconductivity.   [SIZE=+1]Levitation in action[/SIZE]A superconductor is immersed in liquid nitrogen to provide cooling below the critical temperature. A magnet is placed in the air above the superconductor and left there levitating. Nothing but magnetic interaction keeps the magnet from falling down. <img src="http://www.fys.uio.no/super/levitation/lev.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />[SIZE=+1]Finding a better levitating position[/SIZE]The levitating magnet has a preferential position above the superconductor and returns there after a small perturbation by a human finger. When the magnet is pushed hard towards the superconductor, it changes the magnetic field distribution in the superconductor, and a new position becomes preferential. <img src="http://www.fys.uio.no/super/levitation/position.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />[SIZE=+1]Lifting superconductor without touching it[/SIZE]At room temperature magnetic field lines from the magnet penetrate the superconductor without restraint. After cooling by liquid nitrogen they get trapped by microscopic inhomogeneities in the superconductor. The trapped magnetic lines then serve as invisible threads holding the two objects together at a certain distance. <img src="http://www.fys.uio.no/super/levitation/up.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />[SIZE=+1]Smooth landing during warming up[/SIZE]When the superconductor is taken out of the liquid nitrogen, its temperature slowly starts increasing. As a result, the superconducting properties weaken, and the levitation force gradually gives way to the gravity. [SIZE=+1]Schematic visualization of magnetic field lines[/SIZE]  Why repulsion? Magnetic field is partly excluded from the superconductor. Hence, the same repulsion as between a magnet and a diamagnetic.  Why attraction? The magnetic flux lines that managed to penetrate the superconductor get pinned (trapped) there by microscopic inhomogeneities. When the magnet is lifted up, the superconductor holds its magnetic lines and follows the magnet. How to help magnetic lines penetrate the superconductor? Place the superconductor close to the magnet already at high temperature or push the magnet hard towards the supercondictors <img src="http://www.fys.uio.no/super/levitation/lines.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />Such a distribution of magnetic field lines is expected for a type-II superconductor with flux pinning, i.e. for all high-temperature superconductors (HTS)</blockquote>

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