Question

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Consider a ferromagnetic material :
Assertion (A): The individual atoms in a ferromagnetic material possess a magnetic dipole moment and interact with one another in such a way that they spontaneously align themselves forming domains.
Reason (R): At high enough temperature, the domain structure of ferromagnetic material disintegrates. Thus, magnetization will disappear at high enough temperature known as Curie temperature.
In the light of the above statements, choose the correct answer from the options given below :

• A. (A) is false but (R) is true
• B. Both (A) and (R) are true but (R) is not the correct explanation of (A)
• C. Both (A) and (R) are true and (R) is the correct explanation of (A)
• D. (A) is true but (R) is false

Hint:

To check if R is the explanation of A, read A, then add "because" followed by R. If it sounds like a logical cause-effect relationship, it's the correct explanation.

Answer 1

The Correct Option is B

Let's analyze the assertion and reason provided:

• Assertion (A): The individual atoms in a ferromagnetic material possess a magnetic dipole moment and interact with one another in such a way that they spontaneously align themselves forming domains.
• Reason (R): At high enough temperature, the domain structure of ferromagnetic material disintegrates. Thus, magnetization will disappear at high enough temperature known as Curie temperature.

Explanation:

• Ferromagnetic materials have atoms with magnetic dipole moments. These atoms align themselves in small regions called domains. This alignment occurs due to the strong exchange interactions between neighboring atomic dipoles, resulting in spontaneous magnetization within each domain. Thus, the assertion is true.
• The behavior of ferromagnetic materials changes with temperature. Below a certain temperature (the Curie temperature), ferromagnetic materials maintain their domain structure, allowing them to be magnetized. However, at temperatures above the Curie temperature, thermal agitation overcomes the magnetic interactions, causing the domain structure to collapse and the material to become paramagnetic. This means the reason is also true.

Analysis of the Correct Answer:

• Both the assertion and the reason are accurate statements regarding ferromagnetic materials and their behavior at different temperatures.
• However, while the reason correctly describes the behavior of ferromagnetic materials at high temperatures and the concept of Curie temperature, it does not directly explain why the domains form initially in ferromagnetic materials, which is the focus of the assertion.

Thus, the appropriate choice is: Both (A) and (R) are true but (R) is not the correct explanation of (A).