Question

A ball of a superconducting material is dipped in to the liquid nitrogen and placed near a bar magnet. In which direction will the ball move then?
(A) away from the bar magnet
(B) towards the bar magnet
(C) around the bar magnet
(D) it remains constant

Answer 1

Superconductivity is a phenomenon whereby a charge moves through a material without resistance. It means if a material is a superconductor then it has zero resistance and the electron moves through them without the need for any potential difference to be applied across the ends of the superconductor. Liquid nitrogen behaves as a superconductor above 77 K.

Complete step by step answer: We are given a superconducting material and it is dipped inside the liquid nitrogen. One point of similarity between both of them is that both are diamagnetic. Diamagnetic materials are those composed of atoms which have no net magnetic moments. They have no permanent magnetic dipole moment.
Thus, superconducting material is also diamagnetic and when it is dipped inside another diamagnetic material the dipped ball of superconductor in liquid nitrogen also behaves as a diamagnetic material. And when it is placed near a bar magnet it gets repelled because diamagnetic materials are weakly repelled by an external magnetic field. Thus, the correct option is (A).

Note: When diamagnetic material is placed in an external magnetic field diamagnetic levitation takes place. The diamagnetic material will repel the material producing the magnetic field. Some examples of diamagnetic materials are Bismuth, carbon, Mercury etc.