Ferromagnetic Materials for Permanent Magnets – Rankers Physics

Magnetic Properties of Matter: Practice Problem & Solution

Assertion (A): Ferromagnetic materials of high retentivity are used to form permanent magnet. Reason (R): Ferromagnetic materials have positive intensity of magnetisation.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Magnetic Properties of Matter. Understanding the underlying formula is key to arriving at the correct answer below:

For a permanent magnet, the material must have high retentivity and high coercivity to retain magnetism. Ferromagnetic materials do exhibit positive intensity of magnetisation, which is true, but this general property is not the direct reason for choosing high retentivity for permanent magnets. Both A and R are true, but R is not the correct explanation of A.

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