/kloc-In the early 9th century, many people were addicted to the manufacture of a mysterious machine-the first perpetual motion machine, because the envisaged machine only needed an initial force to make it work, and then it could automatically and continuously do work without any power or fuel. Before the first law of thermodynamics was put forward, people had a heated discussion on the possibility of making perpetual motion machines.

It was not until the first law of thermodynamics was discovered that the myth of the first perpetual motion machine was broken.

The first law of thermodynamics is the concrete expression of the law of conservation and transformation of energy in thermodynamics, which shows that heat is a form of material movement. This shows that the energy (heat) transmitted by the outside world to the material system is equal to the sum of the increase of internal energy and the work done by the system. It denies that energy is born out of nothing, so the first perpetual motion machine that can do work without power and fuel becomes a fantasy.

The first law of thermodynamics came into being at the end of 18 and the beginning of 19. With the wide application of steam engines in production, people pay more and more attention to the transformation of heat and work. Thus, thermodynamics came into being. 1798, Thompson denied the existence of thermal mass through experiments. German doctor and physicist Meyer in 184 1? In 843, the idea of mutual transformation between heat and mechanical motion was put forward, which was the first time that the first law of thermodynamics was put forward. Joule designed an experiment to measure the electrothermal equivalent and mechanical equivalent of heat, and determined the first law of thermodynamics through the experiment, which supplemented Meyer's argument.

After the first law of thermodynamics, people began to consider the efficiency of converting thermal energy into work. At this time, someone designed such a machine-it can infinitely take heat from a heat source to do work. This is called the second perpetual motion machine.

1824, French army engineer Carnot conceived an ideal heat engine that did no external work and had no friction. By studying the simple cycle of heat and work (Carnot cycle) between two heat sources with different temperatures in this heat engine, it is concluded that the heat engine must do work between the two heat sources, and the efficiency of the heat engine depends only on the temperature difference with the heat sources. Even in an ideal state, the efficiency of a heat engine cannot reach 100%. That is, heat cannot be completely converted into work.

1850, Clausius unified the law of conservation and transformation of energy and Carnot principle on the basis of Carnot, and pointed out that it is impossible for automatic machines to transfer heat from low-temperature objects to high-temperature objects without change, which is the second law of thermodynamics. Soon, Kelvin suggested that it is impossible to obtain heat from a single heat source, making it completely useful without other effects; In other words, it is impossible to use inanimate machines to cool any part of matter below the lowest temperature around, thus obtaining mechanical work. This is the Kelvin expression of the second law of thermodynamics. Ostwald put it this way: The second perpetual motion machine cannot be built successfully.

Clausius put forward the concept of entropy S=Q/T while putting forward the second law, and expressed the second law of thermodynamics as: in an isolated system, the actual process always increases the entropy of the whole system. However, after that, Clausius mistakenly extended the law of entropy increase of isolated systems to the whole universe, thinking that in the whole universe, heat constantly changed from high temperature to low temperature until there was no temperature difference at a certain moment, and the total entropy of the universe reached a maximum. At this time, there will be no power to transfer heat. This is the so-called "theory of heat death".

In order to refute "theory of heat death", Maxwell imagined an invisible soul (Maxwell Demon), which was by a door in a box. It allows fast particles to reach one side of the box through the door and slow particles to reach the other side of the box through the door. In this way, after a period of time, there will be a temperature difference on both sides of the box. Maxwell demon is actually a prototype of dissipative structure.

1877, Boltzmann discovered the relationship between macroscopic entropy and thermodynamic probability of system S=KlnQ, where k is Boltzmann constant. 1906, Nernst put forward △S/O = 0 when the temperature is close to absolute zero T→0, that is, "Nernst thermal principle". On the basis of Nernst's research, Planck pointed out that the perfect crystal of various substances has zero entropy (S 0 = 0) at absolute zero, which is the third law of thermodynamics.

The three laws of thermodynamics are collectively called the basic laws of thermodynamics. Since then, the thermodynamic foundation has been basically completed.