Question

Given below are two statements:

Statement – I: Permeability of paramagnetic and ferromagnetic substances increase with decrease in temperature.

Statement – II: Diamagnetism is a result of orbital motions of electrons developing magnetic moments opposite to the applied magnetic field.

Choose the correct answer from the options given below:

• A. Both Statement – I and Statement – II are true
• B. Both Statement – I and Statement – II are false
• C. Statement – I is true but Statement – II is false
• D. Statement – I is false but Statement – II is true

Answer 1

Answer: (A)

Both Statement – I and Statement – II are true

Answer 2

Statement I Explanation:

• Paramagnetic Substances: The magnetic susceptibility ($\chi$) follows Curie's Law: $\chi = C/T$, where $C$ is the Curie constant and $T$ is the absolute temperature. As $T$ decreases, $\chi$ increases. Permeability ($\mu$) is related to susceptibility by $\mu = \mu_0 (1 + \chi)$. Therefore, as $\chi$ increases, $\mu$ also increases.

• Ferromagnetic Substances: Below the Curie temperature ($T_C$), stronger alignment of magnetic domains occurs as temperature decreases, significantly increasing susceptibility and permeability. Above $T_C$, they behave paramagnetically, following the Curie-Weiss law: $\chi = C/(T - T_C)$, implying increased susceptibility as temperature approaches $T_C$.

Statement II Explanation:

Diamagnetism arises from the orbital motion of electrons. An external magnetic field induces a change in this motion, creating an induced magnetic moment that opposes the applied field, as described by Lenz's Law. This results in weak repulsion from the magnetic field.