Arrange the following substances in ascending order of their relative…

The correct answer is Option (1) → (D), (B), (C), (A)

Relative permeability \( \mu_r = \mu/\mu_0 \) tells how much a material strengthens (\( \mu_r \gt 1 \)) or weakens (\( \mu_r \lt 1 \)) a magnetic field placed in it. A superconductor expels the field completely (the Meissner effect), so B = 0 inside it and \( \mu_r = 0 \). The types of magnetic material follow in order: diamagnetic substances have \( \mu_r \) slightly less than 1, paramagnetic substances slightly more than 1, and ferromagnetic substances very much more than 1.

    \( \text{(D) superconductor: } \mu_r = 0 \)
    \( \text{(B) nitrogen (diamagnetic): } \mu_r \lt 1 \)
    \( \text{(C) oxygen (paramagnetic): } \mu_r \gt 1 \)
    \( \text{(A) nickel (ferromagnetic): } \mu_r \gg 1 \)

So the ascending order is (D), (B), (C), (A).

NCERT (2026-27):
Diamagnetism – “… Some diamagnetic materials are bismuth, copper, lead, silicon, nitrogen (at STP), water and sodium chloride.”

Diamagnetism – “… The most exotic diamagnetic materials are superconductors. … Here the field lines are completely expelled! χ = –1 and μ_r = 0.”

Paramagnetism – “… Some paramagnetic materials are aluminium, sodium, calcium, oxygen (at STP) and copper chloride.”

Ferromagnetism – “… There are a number of elements, which are ferromagnetic: iron, cobalt, nickel, gadolinium, etc. The relative magnetic permeability is >1000!”

Summary – “… 7. Magnetic materials are broadly classified as: diamagnetic, paramagnetic, and ferromagnetic. For diamagnetic materials χ is negative and small and for paramagnetic materials it is positive and small. Ferromagnetic materials have large χ.”