Q142 / 180 · AIIMS 2004 · Physics

Assertion : A disc-shaped magnet is leviated above a superconducting material that has been cooled by liquid nitrogen. Reason : Superconductors repel a magnet.

  • Correct answer
    A
    If both assertion and reason are true and reason is the correct explanation of assertion
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion
  • C
    If assertion is true but reason is false
  • D
    If both assertion and reason are false.

Solution

Since superconductors exist only below a certain critical temperature and above that temperature they behave like normal materials. When magnet is placed above superconductor and cooled using liquid nitrogen. The induced magnetic field inside the superconductor is exactly equal and opposite in direction to the applied magnetic field, so that they cancel within the super conductor. These poles will repel each other and the force of repulsion is enough to float the magnet.

Hence, the correct answer is option: 'A'.

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