Reversible and Irreversible Process:-

Reversible Process:-

It is a process which can be made to proceed in the reverse direction by a very slight change in its conditions so that the system passes through the same states as in direct process, and at the conclusion of which the system and its surroundings acquire the initial conditions.

All isothermal and adiabatic process when allowed to proceed slowly, are reversible, provided there is no loss of energy against any type of resistance i.e., friction, viscosity etc. Below are the locus of isothermal, isobaric, isochoric and adiabatic process. 

Examples of some reversible process:-

(i) One gram of ice at 0°C requires 80 cal of heat to be converted into water at 0°C. Same amount of heat when taken out of water will convert it back to ice. So, fusion of ice is a reversible process.

(ii) One gram of water at 100°C gets converted into steam at 100°C by gaining 536 cal of heat. Same amount of heat when taken out of steam converts it back to water. So, vaporization of water is also a reversible process.

(iv) Passage of electric current through a thermo-couple creates some temperature difference between the two junctions. Temperatures of the two junctions get reversed on reversing the direction of electric current. So ‘Peltier effect’ is also a reversible process.

Following basic conditions have to be fulfilled for a process to be reversible:-

(a) The change must take place at a very slow rate.

(b) There should be no loss of energy due to the conduction or convection or dissipation of energy against any resistive effect like friction, viscosity etc.

(c) No heat should be converted  into magnetic or electric energy.

(d) The system must always be in thermal and mechanical equilibrium with the surrounding.

Irreversible Process:-

A process which cannot be made to be retraced in opposite direction by reversing the controlling factor is called an irreversible process.

The conditions mentioned above for the realisation of a reversible process are difficult to be met with, practically, since in every process some loss of energy is going to take place for one reason or the other. So most of the processes we come across in our daily life are irreversible processes. 

Examples of some irreversible process:-

(i) Work done against friction.

(ii) Joule’s heating effect.

(iii) Diffusion of gases into another.

(iv) Magnetic hysteresis.

 

Related Resources: 

Click here for the Detailed Syllabus of IIT JEE Physics.

Look into the Sample Papers of Previous Years to get a hint of the kinds of questions asked in the exam.

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