The Clausius statement is related to the everyday observation that heat never flows spontaneously from a cold object to a hot object. Thus, the Clausius statement becomes: It is impossible to construct a refrigerator that transfers heat from a cold reservoir to a hot reservoir without aid from an external source. We can show that the Kelvin statement is equivalent to the Clausius statement if we view the two objects in the Clausius statement as a cold reservoir and a hot reservoir. Neither of these devices is achievable in reality. (b) A “perfect refrigerator” transports heat from a cold reservoir to a hot reservoir without work input. (a) A “perfect heat engine” converts all input heat into work. The first law does not exclude the possibility of constructing a perfect engine, but the second law forbids it. Despite advancing technology, we are not able to build a heat engine that is efficient. The Kelvin statement is a manifestation of a well-known engineering problem. However, if the gas were returned to its initial state (that is, made to complete a cycle), it would have to be compressed and heat would have to be extracted from it. Another example is a chamber of gas that can absorb heat from a heat reservoir and do work isothermally against a piston as it expands.
Without completing a cycle, the substance in the engine is not in its original state and therefore an “other effect” has occurred. For example, an engine can absorb heat and turn it all into work, but not if it completes a cycle. Note that “without any other effect” is a very strong restriction. This statement describes an unattainable “ perfect engine,” as represented schematically in (Figure)(a). This is known as the Kelvin statement of the second law of thermodynamics. It is impossible to convert the heat from a single source into work without any other effect. Now let’s get straight into the examples of second law of thermodynamics.Second Law of Thermodynamics (Kelvin statement) If you are facing difficulty in understanding the above statements of second law, then kindly refer to this article “ Detailed explanation on second law of thermodynamics“, where I’ve explained these statements in a very simple way.
“Heat can not itself flow from colder body to a hotter body.” “It is impossible to construct a device (operating in a cycle) that can transfer heat from cold body to the hot body without absorbing any work.”
“It is impossible to construct a device (operating in a cycle) which works on a single heat source and converts all of its heat completely into work” “In all the spontaneous processes, the entropy of the universe increases.” So let me share with you some glimpse of the statement of second law of thermodynamics here only.Įntropy statement of Second law of thermodynamics: I know you will not visit this above article. If you do not know anything about the second law of thermodynamics then I suggest you to refer this detailed article on the second law of thermodynamics which will make you understand all the three statements of the 2nd law. Well, let’s get started with some amazing real life examples of second law of thermodynamics. I’ll just show you the images like this and you are done with all the examples. All the examples of second law of thermodynamics are very easy. While it can not become hot again on its own.