The law of conservation and the transformation of energy is one of the most important postulates of physics. Consider the history of its appearance, as well as the main areas of application.
History Pages
First, let's find out who discovered the law of conservation and transformation of energy. In 1841, the English physicist Joule and the Russian scientist Lenz conducted experiments in parallel, as a result of which the scientists managed to find out in practice the connection between mechanical work and heat.
Numerous studies conducted by physicists in different parts of our planet predetermined the discovery of the law of conservation and transformation of energy. In the middle of the nineteenth century, the German scientist Mayer gave his formulation. The scientist tried to summarize all the information about electricity, mechanical movement, magnetism, human physiology that existed at that time.
Around the same period, similar thoughts were expressed by scientists in Denmark, England, Germany.
Experiments withwarmth
Despite the variety of ideas concerning heat, a complete picture of it was given only to the Russian scientist Mikhail Vasilyevich Lomonosov. Contemporaries did not support his ideas, they believed that heat was not associated with the movement of the smallest particles that make up matter.
The law of conservation and transformation of mechanical energy, proposed by Lomonosov, was supported only after Rumfoord managed to prove the presence of motion of particles inside matter during experiments.
To obtain heat, the physicist Davy tried to melt ice by rubbing two pieces of ice against each other. He put forward a hypothesis according to which heat was considered as an oscillatory motion of particles of matter.
Mayer's law of conservation and transformation of energy assumed the immutability of the forces that cause the appearance of heat. This idea was criticized by other scientists, who reminded that force is related to speed and mass, therefore, its value could not remain unchanged.
At the end of the nineteenth century, Mayer summarized his ideas in a pamphlet and tried to solve the actual problem of warmth. How was the law of conservation and transformation of energy used at that time? In mechanics, there was no consensus on how to obtain, transform energy, so this question remained open until the end of the nineteenth century.
Feature of the law
The law of conservation and the transformation of energy is one of the fundamental ones, allowingcertain conditions to measure physical quantities. It is called the first law of thermodynamics, the main object of which is the conservation of this value in an isolated system.
The law of conservation and transformation of energy establishes the dependence of the amount of heat on various factors. In the course of experimental studies conducted by Mayer, Helmholtz, Joule, various types of energy were distinguished: potential, kinetic. The combination of these species was called mechanical, chemical, electrical, thermal.
The law of conservation and transformation of energy had the following formulation: "The change in kinetic energy is equal to the change in potential energy."
Mayer came to the conclusion that all varieties of this quantity are capable of transforming into each other if the total amount of heat remains unchanged.
Mathematical expression
For example, as a quantitative expression of the law, the chemical industry is the energy balance.
The law of conservation and transformation of energy establishes a relationship between the amount of thermal energy that enters the zone of interaction of various substances, with the amount that leaves this zone.
The transition from one type of energy to another does not mean that it disappears. No, only her transformation into another form is observed.
At the same time, there is a relationship: work - energy. The law of conservation and transformation of energy assumes the constancy of this quantity (its totalquantity) for any processes occurring in an isolated system. This indicates that in the process of transition from one species to another, quantitative equivalence is observed. In order to give a quantitative description of different types of motion, nuclear, chemical, electromagnetic, thermal energy was introduced in physics.
Modern wording
How is the law of conservation and transformation of energy read today? Classical physics offers a mathematical notation of this postulate in the form of a generalized equation of state for a thermodynamic closed system:
W=Wk + Wp + U
This equation shows that the total mechanical energy of a closed system is defined as the sum of kinetic, potential, internal energies.
The law of conservation and transformation of energy, the formula of which was presented above, explains the invariance of this physical quantity in a closed system.
The main disadvantage of mathematical notation is its relevance only for a closed thermodynamic system.
Open systems
If we take into account the principle of increments, it is quite possible to extend the law of conservation of energy to non-closed physical systems. This principle recommends writing mathematical equations related to the description of the state of the system, not in absolute terms, but in their numerical increments.
To fully take into account all forms of energy, it was proposed to add to the classical equation of an ideal systemthe sum of energy increments that are caused by changes in the state of the analyzed system under the influence of various forms of the field.
In the generalized version, the equation of state is as follows:
dW=Σi Ui dqi + Σj Uj dqj
This equation is considered the most complete in modern physics. It was it that became the basis of the law of conservation and transformation of energy.
Meaning
In science there are no exceptions to this law, it governs all natural phenomena. It is on the basis of this postulate that one can put forward hypotheses about various engines, including refutation of the reality of the development of a perpetual mechanism. It can be used in all cases where it is necessary to explain the transitions of one type of energy to another.
Mechanical applications
How is the law of conservation and transformation of energy read at the present time? Its essence lies in the transition of one type of this quantity to another, but at the same time its overall value remains unchanged. Those systems in which mechanical processes are carried out are called conservative. Such systems are idealized, that is, they do not take into account friction forces, other types of resistance that cause mechanical energy dissipation.
In a conservative system, only mutual transitions of potential energy into kinetic energy occur.
The work of forces that act on a body in such a system is not related to the shape of the path. Its valuedepends on the final and initial position of the body. As an example of forces of this kind in physics consider the force of gravity. In a conservative system, the value of the work of a force in a closed section is zero, and the law of conservation of energy will be valid in the following form: “In a conservative closed system, the sum of the potential and kinetic energy of the bodies that make up the system remains unchanged.”
For example, in the case of a free fall of a body, potential energy changes into a kinetic form, while the total value of these types does not change.
In closing
Mechanical work can be considered as the only way of mutual transition of mechanical motion into other forms of matter.
This law has found application in technology. After turning off the car engine, there is a gradual loss of kinetic energy, followed by a stop of the vehicle. Studies have shown that in this case, a certain amount of heat is released, therefore, the rubbing bodies heat up, increasing their internal energy. In the case of friction or any resistance to movement, a transition of mechanical energy into an internal value is observed, which indicates the correctness of the law.
Its modern formulation looks like: “The energy of an isolated system does not disappear into nowhere, does not appear from nowhere. In any phenomena that exist within the system, there is a transition of one type of energy to another, transfer from one body to another, withoutquantitative change.”
After the discovery of this law, physicists do not leave the idea of creating a perpetual motion machine, in which, in a closed cycle, there would be no change in the amount of heat transferred by the system to the surrounding world, in comparison with the heat received from outside. Such a machine could become an inexhaustible source of heat, a way to solve the energy problem of mankind.
