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.
Match List-I with List-II.
| List-I | List-II |
|---|---|
| (A) Field lines are completely expelled from it | (I) Soft iron |
| (B) A ferromagnet that stays magnetised after the external field is removed | (II) Aluminium |
| (C) A ferromagnet that loses its magnetisation when the external field is removed | (III) Superconductor |
| (D) The field inside it is slightly enhanced | (IV) Alnico |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
(A) Field lines are completely expelled from it — This matches (III) Superconductor. A superconductor shows perfect diamagnetism, with \( \chi=-1 \).
(B) A ferromagnet that stays magnetised after the external field is removed — This matches (IV) Alnico. Alnico is a hard ferromagnet, so it is used to make permanent magnets.
(C) A ferromagnet that loses its magnetisation when the external field is removed — This matches (I) Soft iron. Soft iron is a soft ferromagnetic material.
(D) The field inside it is slightly enhanced — This matches (II) Aluminium. Aluminium is paramagnetic, so the field lines get a little concentrated inside it.
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! χ= –1 and μr = 0. …”
Ferromagnetism – “… In some ferromagnetic materials the magnetisation persists. Such materials are called hard magnetic materials or hard ferromagnets. Alnico, an alloy of iron, aluminium, nickel, cobalt and copper, is one such material. …”
Ferromagnetism – “… On the other hand, there is a class of ferromagnetic materials in which the magnetisation disappears on removal of the external field. Soft iron is one such material. …”
Paramagnetism – “… The field lines gets concentrated inside the material, and the field inside is enhanced. In most cases, this enhancement is slight, being one part in 105. …”
Paramagnetism – “Some paramagnetic materials are aluminium, sodium, calcium, oxygen (at STP) and copper chloride. …”