Which of the following statements is correct?

The correct answer is Option (1) → Materials exhibiting Meissner effect are diamagnetic and have \( \chi=-1 \) and \( \mu_r=0 \).

The magnetic behaviour of a material is described by its susceptibility \( \chi \) and relative permeability \( \mu_r = 1 + \chi \). Each option is judged on that basis.

Option (1) — Correct. A superconductor expels the magnetic field completely (the Meissner effect), so it is a perfect diamagnet with \( \chi = -1 \) and \( \mu_r = 1 + \chi = 0 \).

Option (2) — Incorrect. Materials that are only weakly magnetised, with a small positive \( \chi \), are paramagnetic. Ferromagnetic materials are strongly magnetised and have a very large \( \chi \).

Option (3) — Incorrect. It is the other way round: a ferromagnet becomes paramagnetic above its Curie temperature.

Option (4) — Incorrect. Superconductors are perfectly diamagnetic, not ferromagnetic. They are repelled by a magnet because \( \chi = -1 \).

NCERT (2026-27):
Diamagnetism – “… The most exotic diamagnetic materials are superconductors. These are metals, cooled to very low temperatures which exhibits both perfect conductivity and perfect diamagnetism. Here the field lines are completely expelled! \( \chi = -1 \) and \( \mu_r = 0 \). … The phenomenon of perfect diamagnetism in superconductors is called the Meissner effect, after the name of its discoverer.”

Paramagnetism – “Paramagnetic substances are those which get weakly magnetised when placed in an external magnetic field.”

Ferromagnetism – “… At high enough temperature, a ferromagnet becomes a paramagnet.”