Magnetism of a bar magnet can be destroyed if it is I. kept in the magnetic meridian. II. placed in a direction opposite to that of the Earth’s horizontal intensity. III. heated to a temperature known as Curie temperature. Select the correct answer using the code given below

Magnetism in a bar magnet is destroyed or significantly altered through processes that disrupt the alignment of magnetic domains. Statement III is correct because heating a magnet to its Curie temperature provides thermal energy that overcomes the exchange interaction, causing a transition from ferromagnetic to paramagnetic behavior, effectively destroying its permanent magnetism. Statement II is also correct; placing a magnet in a direction opposite to the Earth's horizontal magnetic intensity (or any strong opposing external field) can lead to demagnetization through the process of magnetic reversal or coercive force. However, Statement I is incorrect; keeping a magnet in the magnetic meridian aligns it with the Earth's natural field lines [2], which actually helps preserve its magnetic orientation rather than destroying it. Therefore, only II and III are valid methods for demagnetization.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 5: Earths Magnetic Field (Geomagnetic Field) > Geomagnetic Poles > p. 72
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 5: Earths Magnetic Field (Geomagnetic Field) > Geomagnetic Reversal > p. 74