Thermodynamics is a branch of physics in whichthe mutual transformation of heat into motion and vice versa. Being a fairly extensive section, this part of applied physics is divided into several different subsections, which include:
- Basic laws of thermodynamics.
- Phase transitions and thermodynamic processes.
- Thermodynamic cycles, etc.
In fact, the laws of thermodynamics are not only its subsection, but also postulates, the basis underlying the section of physics under study. Three thermodynamic principles are distinguished.
Let us consider them in more detail.
1. The first law or the beginning of thermodynamics.First we recall that energy is constantly changing from one species to another. Transforming, depending on the conditions, from kinetic to potential and back, energy from the system does not go away. However, an uncomplicated example of a pendulum that was given acceleration casts doubt on this theory. Being in motion, the pendulum has kinetic energy, at the extreme points of the amplitude - the potential. Theoretically, such a movement should not have an end and an edge, that is, be infinite. In practice, we see that the movements are gradually fading, the pendulum stops its course. This is due to the resistance of the air, which determines the friction force when moving. As a result, the energy that was supposed to give the pendulum acceleration is spent on overcoming the air obstacle. As a result, heat is generated. According to the experiments of scientists, the temperature of the suspension and the environment is increased due to the chaotic motion of the molecules of the substance of the pendulum and air.
Actually, the first law of thermodynamics is better known as Law of energy conservation. Its essence lies in the fact that the energy in the system does not disappear, but only transforms from one type into another and passes from one form to another.
For the first time such an observation was described inthe middle of the nineteenth century. K. Morom. He noted that energy can transfer to other states: heat, electricity, traffic, magnetism, etc. However, the law was formulated only in 1847 by Helmholtz, and in the twentieth century. he was awarded the notorious formula E = mc2, which also included the conclusions of A. Einstein.
2. The second law or the beginning of thermodynamics.Formed in 1850 by the scientist R. Clausius, it consists in the following observation: the internal energy distribution in a closed system varies chaotically in such a way that the useful energy decreases, resulting in increased entropy.
3. The third law or the beginning of thermodynamics.Bearing in mind the notion that heat is a disorderly and chaotic motion of molecules, it can be concluded that cooling the system entails a decrease in their motor activity. Entropy is zero in the case when all chaotic motion of molecules is completely stopped.
The absolute value of the entropy of matter can becalculate, knowing its specific heat at absolute zero. V. Nernst by long and numerous studies it was found that all crystalline substances have the same heat capacity: at absolute zero, and it is zero. This conclusion is the third law of thermodynamics. Knowing this fact, one can compare the entropy of various materials with temperature changes.
There is also the so-called zero law of thermodynamics, zIt consists in the following: the heat from the heated part of the isolated system extends to all its elements. Thus, over time, the temperature within the same system is equalized.
The laws of thermodynamics are the basic components of the science of mechanics. Thanks to the findings made at different times, modern science and society have been enriched by the invention of most machines.
The laws of thermodynamics are universal for all branches of mechanics.
