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Physics Guru is an online education and competitive examinations preparation portal founded by Manish Verma, an IIT Madras alumnus, providing learning resources for competitive examinations.

The emphasis is on conceptual understanding, analytical thinking and problem solving rather than simply memorising formulas and standard methods.

The objective is to help students understand what they are learning and develop the ability to solve problems they have not seen before.

Levitating Disk

I think the black object is made of superconducting material which works as superconductor at a temperature above the temperature of the liquid Nitrogen (B.P. -196°C). The disk is a magnet. When the magnet is moved towards the black object it causes eddy currents in it due to induction which die down soon due to the internal resistance when liquid Nitrogen in not poured. However, when liquid Nitrogen is poured the temperature falls and falls enough for the black object to behave like a superconductor. Now, when the magnet is moved causing eddy currents then they don't die down quickly and the magnetic field produced by them opposes the magnet (disc) by Lenz's law and the magnet hangs.

This phenomenon looks different from that of the levitating frog which is due to the diamagnetism.