A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:
(A) Decrease in size and changes orientation.
(B) May increase or decrease in size and change its orientation.
(C) Increase in size but no change in orientation.
(D) Have no relation with external magnetic field.

Hint:In order to solve this question, we should know the meaning of ferromagnetism. The term ferromagnetism is taken from the word ‘ferrous’ which means iron, which is the first metal that is known to exhibit attractive properties to the magnetic fields. It is a special behaviour that is shown by certain materials like alloys, cobalt, iron, etc.

Complete answer:
The atoms of ferromagnetic materials in their unmagnetized state form domains inside the ferromagnetic materials and these domains have large magnetic moments of atoms. These domains have magnetic moments in different directions in the absence of a magnetic field. Even then when the magnetic field is applied, the domains aligned in the same direction as the field grow in size and those aligned in the direction opposite to the field usually reduce in size and the orientation changes too.

When a soft ferromagnetic material is kept in an external magnetic field, the magnetic domains may usually increase or decrease in size and change its orientation.

Therefore, Option B is the correct answer.

Note: Ferromagnetic materials are groups of substances, which tend to display strong magnetism in the direction of the field due to the application of a magnetic field. The cause of magnetism in these materials is mainly due to the alignment patterns present in their constituent atoms. These atoms usually tend to behave as an elementary electromagnet.