Case: Read the passage and answer the question.
In terms of the susceptibility, we can classify materials as diamagnetic, paramagnetic or ferromagnetic. Diamagnetic substances are those which have a tendency to move from the stronger to the weaker part of an external magnetic field. In other words, unlike the way a magnet attracts metals like iron, it would repel a diamagnetic substance. Paramagnetic substances are those which get weakly magnetised when placed in an external magnetic field. They have a tendency to move from a region of weak magnetic field to a region of strong magnetic field, i.e., they get weakly attracted to a magnet. Ferromagnetic substances are those which get strongly magnetised when placed in an external magnetic field. They have a strong tendency to move from a region of weak magnetic field to a region of strong magnetic field, i.e., they get strongly attracted to a magnet.
Which of the following has the highest magnetic susceptibility?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Ferromagnetic substances
The magnetic susceptibility \( \chi \) shows how strongly an external field magnetises a material (\( M=\chi H \)). The passage groups the three classes by how strongly they get magnetised. The value of \( \chi \) follows the same order.
Option (1) Diamagnetic substances — Incorrect. A magnet repels them because their magnetisation is opposite to the field. So their susceptibility is negative.
Option (2) Paramagnetic substances — Incorrect. They get only weakly magnetised along the field, so their susceptibility is positive but small.
Option (3) Ferromagnetic substances — Correct. They get strongly magnetised along the field, and a magnet attracts them strongly. So their susceptibility is large and positive, the highest of the three.
NCERT (2026-27):
Magnetic Properties of Materials – “… In terms of the susceptibility χ, a material is diamagnetic if χ is negative, para- if χ is positive and small, and ferro- if χ is large and positive.”