Question
Answer the following question:
Explain qualitatively on the basis of domain picture the irreversibility in the magnetisation curve of a ferromagnet.
Solution
The atomic dipoles are grouped together in domains in a ferromagnetic substance. All the dipoles of a domain are aligned in the same direction and, have a net magnetic moment. In an unmagnetised substance these domains are randomly distributed so that the resultant magnetisation is zero.
When the substance is placed in an external magnetic field the domains, tend to align themselves in the direction of the field. Some energy is spent in the process of alignment. These domains do not come back into their original random positions completely when the external field is removed.
A part of the magnetisation is retained by the substance. The energy spent in the process of magnetisation is not fully recovered. The balance of energy is lost as heat. This has been found as the basic cause for irreversibility of the magnetisation curve of a ferromagnetic substance.
When the substance is placed in an external magnetic field the domains, tend to align themselves in the direction of the field. Some energy is spent in the process of alignment. These domains do not come back into their original random positions completely when the external field is removed.
A part of the magnetisation is retained by the substance. The energy spent in the process of magnetisation is not fully recovered. The balance of energy is lost as heat. This has been found as the basic cause for irreversibility of the magnetisation curve of a ferromagnetic substance.
