Question

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because:

• A. domains get oriented randomly
• B. domains are not afftected by magnetic field
• C. all the domains get oriented in the direction of magnetic field
• D. all the domains get oriented in the direction opposite to the direction of magnetic field

Answer 1

The correct option is C all the domains get oriented in the direction of magnetic field

Ferromagnetic substance:
It is a property by which a substance can show permanent magnetism even in the absence of the magnetic field. Such substance are known as ferromagnetic substances.
These substances are strongly attracted by an applied magnetic field and can be permanently magnetised.

In solid state, the metal ions are grouped together in small regions called domains, each such domain acts as a tiny magnet.
These are randomly oriented in an unmagnetized piece of the substance.
For ferromagnetic substance, in presence of an applied field, domains get aligned with the applied magnetic field. The combined effect of the atomic magnetic moments results in a relatively large magnetization. These ordered domains persist even after removing the external magnetic field. Thus, it becomes a permanent magnet.
Thus, option (a) is correct.