Thermodynamics is a branch of physics that studies the mutual conversion 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 that underlies the studied branch of physics. In total, three thermodynamic principles are distinguished.
Let's consider them in more detail.
1. The first law or the beginning of thermodynamics. First, remember that energy is constantly moving from one species to another. Transforming, depending on the conditions, from kinetic to potential and vice versa, energy does not leave the system. However, a simple example of a pendulum that has been given acceleration casts doubt on this theory. While in motion, the pendulum has kinetic energy, at the extreme points of the amplitude - potential. Theoretically, such a movement should not have an end and an edge, that is, be infinite. In practice, we see that the movements gradually fade away, the pendulum stops its course. This happens due to air resistance, which determines the friction force during movement. As a result, the energy that was supposed to give the pendulum acceleration is spent on overcoming an air obstacle. As a result, heat is generated. According to the experiments of scientists, the temperature of the suspension and the environment rises due to the random movement of the molecules of the substance of the pendulum and air.
Actually, the first law of thermodynamics is better known as the law of conservation of energy. Its essence is that the energy in the system does not disappear, but only is converted from one form to another and passes from one form to another.
This observation was first described in the middle of the 19th century. K. Morom. He noted that energy can pass into other states: heat, electricity, motion, magnetism, etc. However, the Law was formulated only in 1847 by Helmholtz, and in the 20th century. he was assigned 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 changes randomly in such a way that the useful energy decreases, resulting in an increase in entropy.
3. The third law or the beginning of thermodynamics. Bearing in mind the notion that heat is the random and random movement of molecules, we can conclude that cooling the system entails a decrease in their motor activity. Entropy is zero when all random motion of molecules is completely stopped.
The absolute value of the entropy of a substance can be calculated by knowing its heat capacity at absolute zero. V. Nernst, through 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 represents the third law of thermodynamics. Knowing this fact, one can compare the entropy of various materials with changes in temperature.
There is also the so-called zero law of thermodynamics , it is included in the following: the heat from the heated part of an isolated system extends to all its elements. Thus, over time, the temperature within the same system equalizes.
The laws of thermodynamics are the basic components of the science of mechanics. Thanks to the conclusions 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.