Let us consider a case when a glass of hot water is placed in a room. Within minutes the water cools off. The heat lost by coffee will equal the amount that will equal the amount that will be absorbed by the surrounding air. Now let’s think of a possible improbable event of hot water getting hotter with the heat getting transferred from the room to the coffee. Now while looking into the two cases we can say that processes can proceed in one direction but not in reverse. The nonfeasibility associated with the reverse process cannot be explained through the first law of thermodynamics.
The inadequacy of the first law as shown above has been remedied with the second law of thermodynamics. The second law which is applicable only in macroscopic objects as suggested by Clausius that “It is impossible to devise an engine which, working in a cycle, shall produce no effect other than the transfer of heat from a colder to a hotter body.” Clausius continued and gave the concept of entropy which suggested that all processes in nature cause some permanent change and termed that change as entropy (Entropy Law, 2001).
Hence the discovery of the two laws of thermodynamics is being regarded as one of the major revolutions in physics in the 19th century. As the subject is concerned with energy and its interaction with matter; the very beginning of associated concepts talks of the eternal existence of energy. While toeing the first law of thermodynamics, one can understand the fact behind the existence of the Universe and various associated entities. The first law states that energy can neither be created nor destroyed and hence the relation and interaction between heat and work can be established. Moving on to the second law of thermodynamics, the point which comes into glare is the impossibility associated with the existence of any continuous process or device that can convert all the thermal energy or heat into work. The most surprising thing related to the above-mentioned two laws of thermodynamics is that of violation and discovery of idea. The second law of thermodynamics has never been violated while the first law of thermodynamics has to be modified when energy production through nuclear reaction comes into the picture. Also, the ideas that led to the discovery of the second law of thermodynamics were discovered earlier to those that led to the development of the first law of thermodynamics (Srinivasan, 2001).
The theory behind this Second Law has its roots in the monograph written by great French researcher Sadi Carnot in the year 1824. It was the time when the first law of thermodynamics was not known but Carnot unfolded all theoretical and practical issues related to the processes which convert thermal energy into mechanical energy while depending on Lavoisier’s caloric theory. Lavoisier’s caloric theory states that heat is nothing but an invisible massless fluid called Caloric and can move from one body to another. This invisible fluid can neither be created nor destroyed. The absence of the concepts related to the law of conservation of energy which later formed the very basis of the first law of thermodynamics, made many scientists of that era believe the concepts of the caloric theory. And hence the caloric theory of heat reigned supreme for more than a century. So in the words of that era, it was assumed that the caloric was neither created nor destroyed, and also this Universe is a vast but limited reservoir of caloric. Another limitation associated with this theory was the very inability it associated with the assumption that mechanical energy cannot be converted to heat (Srinivasan, 2001).
The above-mentioned myth received a crack late in 1798 with Count Rumford categorically demonstrated the possibility of converting mechanical energy to heat through the use of cannon during boring. Though he couldn’t derive any relationship between mechanical and thermal energy and hence didn’t convince the believers in the caloric theory. Later, Robert Mayer proposed the concepts that correlated the various forms of energy and in a simple statement said that thermal and mechanical energy are different forms of the same energy. He also gave a rough estimate of the relationship between heat and work but his ideas were not accepted. But a series of good experiments done by James Prescott Joule and Kelvin provided the much-needed elegance to the experiments that proved the similar nature of heat and other forms of energy and in the second half of the 19th century, the quantitative relationship between mechanical and thermal energy was developed and made an end to the existence of Caloric theory (Srinivasan, 2001).
But Carnot after analyzing the working of the water wheel and the concept of conversion of potential energy into kinetic concluded that the steam engine can produce motive power due to the consumption of caloric but due to its transportation from the warmer body to the cold one. The capacity or power of these steam engines depends a lot on the quantity of caloric involved. The larger the quantity transferred the more is the capacity of the engine. So the Caloric theory-based explanation of this law of thermodynamics as given by Carnot is still sufficiently applicable even though the caloric theory has now been discredited (Srinivasan, 2001).
Lord Kelvin gave a very technical explanation of the second law of thermodynamics. He stated that the processes involved are irreversible. His interpretation included the fact that the entropy is always increasing and the universe might enter into a state of uniform temperature with maximum possible entropy and zero possibility of extracting any work (Weisstein, 2007). While referring to the second law of thermodynamics, Max Planck stated that it is not possible to create a perpetual motion machine. Though numerous attempts have been made to create a perpetual machine as Planck has already mentioned; it’s impossible to create the same. History has seen an innumerable number of perpetual-motion machines on paper but none of them ever seen a physical existence. A perpetual motion machine working on a cycle and exchanging heat with a single reservoir satisfies the first law but violates the second law (hp-granite, 2004).
In the words of Sadi Carnot, the great French Physicist of the 19th century, “The production of motive power is then due in steam engines not on actual consumption of the caloric but to its transportation from a warm body to cold body” (Srinivasan, 2001). Carnot’s effort in explaining the functioning of the steam engine that too depending on Caloric theory led to the roots of second law even before the first law had come into existence. The Carnot’s effort was later underlined by Clausius, Kelvin, and Plank. Clausius introduced the term entropy and make this law more meaningful. Kelvin expanded the scope of entropy and called it an ever-increasing quantity. Plank proved the truthfulness of the law and shrugged aside all the efforts and claims behind the existence of a perpetual motion machine.
The second law of thermodynamics and its development; have been very unusual. It was discovered by Carnot while depending on Caloric Theory. The caloric theory was later found to be discredited but the second law didn’t lose its truthfulness. The other most interesting part is that it has found its existence even before the first law was searched (Srinivasan, 2001). The search for a perpetual motion machine that can defy the second law of thermodynamics continued for a very long period in history but none of them ever came into existence. The efforts of Carnot, Clausius, and later that of Plank and Kelvin made a very descriptive explanation of the law and the nonexistence of any perpetual motion machine.
Bibliography
- Entropy Law (2001). All about Entropy, the laws of Thermodynamics, and Order from Disorder. Archives of Science. [online]. Web.
- hp-gramatke (2004). Perpetuum Mobile-Science. [online]. Web.
- Srinivasan, J. (2001). Sadi Carnot and the Second Law of Thermodynamics. Resonance- journal of science education, Indain Academy of Science [online]. Web.
- Weisstein, E. W. (2007). Kelvin, Lord William Thomson (1824-1907).Eric Weisstein: World of Biography. [online]. Web.