Consider the following processes:

1. Extension of a spring

2. Plastic deformation of a material

3. Magnetization of a material exhibiting hysteresis

Which of the above processes are irreversible?

Explanation:

• Any process is said to be irreversible if the system and surrounding are not restored to initial condition without leaving net effect on the surrounding.
• The spring after extension will come back to its original position after removal of load, hence it can be considered as reversible.
• When the material is deformed plastically then the retrieval path means the amount of energy which gas given to deform it if it is removed from the material then the material will not come to the initial state therefore it is an irreversible process.
• When a material showing hysteresis is magnetized, the magnetization is obtained by applying a large field to the specimen and then removing it.
• When the magnetic field is decreased and the reverses in sign, the magnetization of a ferromagnetic material does not retrace its original path of values. Therefore it is an irreversible process.