Entropy Principle: Applications?

Welcome back MechanicalEI, 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 classusius provides the criterion for reversibility of the cycle. If R equals 0, the cycle is reversible, if R is less than zero then the cycle is irreversible but possible, if R is greater than zero 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 thus indicates the direction in which a process takes place. A process occurs in such a direction as to cause an increase in entropy of the universe. After establishing these facts we move to look at a simple application of the entropy principal: Consider the transfer of heat through a finite temperature difference. If you write the equation for entropy, We realise that entropy change is only positive and zero for the cases where T1T2 and T1=T2. Also, it's negative for T1T2 implying that the transfer can only take place in that direction. Hence, this easy example of heat transfer easily depicts how entropy and in turn second law governs the transfer of energy.

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