It requires external work to carry out the process against the nature that is from lower to higher potential. Entropy and Second Law of ThermodynamicsĪs per second law of thermodynamics, all the spontaneous processes occur in the nature from higher to lower potential. When the system reaches equilibrium the increase in entropy becomes zero. Thus the entropy of the isolated system tends to go on increasing and reaches maximum value at the state of equilibrium. The entropy of the world tends towards a maximum. The energy of the world (universe) is constant. Summarizing the first and second law of thermodynamics, Clausius made two statements: The reverse occurs when the heat is removed from the system.” When the heat is imparted to a system, the disorderly motion of the molecules increases and so the entropy of the system increases. It may be roughly said that the entropy of a system is a measure of degree of molecular disorder existing in the system. ![]() So there is link between entropy and disorder. An isolated system always tends to a state of greater entropy. In his book Engineering Thermodynamics, the author P K Nag says, “An irreversible process always tends to take the isolated system to a state of greater disorder. Here let us keep in mind that isolated system can always be formed by including any system and surroundings within a single boundary. This means the certain amount of the irreversibility is always there in the system, this also means that the entropy of the isolated system always goes on increasing, it never reduces. As such the reversible process is an ideal process and it never really occurs. More is the irreversibility more increase is the entropy of the system. The entropy of the isolated system is the measure of the irreversibility undergone by the system. This causes irreversiblities inside the system and an increase in its entropy. Internal changes in the system: Due to internal changes in the movements of the molecules of the system there is further disturbance inside the system. Any change in the heat content of the system leads to disturbance in the system, which tends to increase the entropy of the system. ![]() Here are the various causes of the increase in entropy of the closed system are:ĭue to external interaction: In closed system the mass of the system remains constant but it can exchange the heat with surroundings. ![]() In actual practice whenever there is change in the state of the system the entropy of the system increases. In actual practice the reversible isentropic process never really occurs, it is only an ideal process. In the previous article on what is entropy, we saw the causes of increase in entropy of the sysem.
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