 Welcome back Mechanical AI. Entropy being a property of the system has many applications. This makes us wonder what are the applications of entropy. Before we jump in check out the third part of this series to find out what entropy is. Now let's clear out a few concepts. The inequality of clauses provides the criterion for reversibility of the cycle. If r equals 0 the cycle is reversible. If r is less than 0 then the cycle is irreversible. But possible. If r is greater than 0 then the cycle is impossible since it violates the second law. The entropy of an isolated system can never decrease. It always increases and remains constant only when the process is reversible. This is known as the entropy principle. The second law does indicates the direction in which a process takes place. That is a process occurs in such a direction as to cause an increase in the entropy of the universe. After establishing these facts we move to look at a simple application of the entropy principle. Consider the transfer of heat through a finite temperature difference. If you write the equation for entropy for this particular case we realize that entropy change is only positive and zero for the cases where T1 is greater than T2 and T1 is equal to T2. Also it's negative for T1 less than T2 implying that the transfer of heat can only take place in that direction. Hence this easy example of heat transfer easily depicts how entropy and in turn the second law governs the transfer of energy. So like, subscribe and comment with your feedback to help us make better videos. Thanks for watching. Also thanks a lot for those constructive comments. You helped the channel grow. So here are the top mechanical EIs of our last videos. In the next episode of Mechanical EI find out what thermodynamic relations are.