Below are mentioned some properties of ferromagnetic substances. Identify the correct ones.
(A) These have strong tendency to move from a region of weak magnetic field to strong magnetic field
(B) In these substances, atomic dipoles align themselves in a common direction over a macroscopic volume called domains
(C) Magnetisation of these materials is inversely, proportional to the absolute temperature \( M \propto \displaystyle\frac{1}{T} \) (Curie's law)
(D) These materials show Meissners effect super conducting magnets which is used in magnetically levitated superfast trains
(E) The temperature of transition from ferromagnetic to paramagnetic is called Curies law
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (B), (E) only
Ferromagnetic substances (iron, cobalt, nickel) are strongly magnetised in the direction of an applied field because their atomic dipoles line up in domains. The ferromagnetic property disappears above a transition temperature.
(A) These have strong tendency to move from a region of weak magnetic field to strong magnetic field — Correct. A ferromagnet is strongly attracted towards the stronger part of a non-uniform field.
(B) In these substances, atomic dipoles align themselves in a common direction over a macroscopic volume called domains — Correct. This is the domain picture of ferromagnetism.
(C) Magnetisation of these materials is inversely, proportional to the absolute temperature \( M \propto 1/T \) (Curie's law) — Incorrect. Curie's law, \( M \propto 1/T \), describes paramagnetic substances, not ferromagnetic ones.
(D) These materials show Meissners effect super conducting magnets which is used in magnetically levitated superfast trains — Incorrect. The Meissner effect (complete expulsion of the field) belongs to superconductors, which are perfectly diamagnetic.
(E) The temperature of transition from ferromagnetic to paramagnetic is called Curies law — Correct. The statement refers to the Curie temperature \( T_C \): above it the domain structure breaks up and a ferromagnet becomes paramagnetic.