You see the take-off missile. She makes a job - raises astronauts and cargo. The kinetic energy rocket is increasing, Since as the rocket is rated, becomes more and more speed. Potential rocket energy also increases Since she rises more and above the earth. Consequently, the sum of these energies, that is Mechanical energy rocket, also increases.

We remember that when the body is performed, its energy decreases. However, the rocket makes work, but its energy does not decrease, but increases! What is the contradiction attendance? It turns out that in addition to mechanical energy, there is another type of energy - internal energy. It is due to the reduction of the internal energy of the combusting fuel rocket commits mechanical work And, moreover, increases its mechanical energy.

Not only gorry, but also hot Bodies have internal energy, which is easy to turn into mechanical work. We do experience. We heat in boiling water and put on a tin box attached to the pressure gauge. As the air in the box will warm up, the liquid in the pressure gauge will start moving (see Figure).

Expanding air performs over liquid operation. Due to the energy, this is happening? Of course, due to the internal energy of Giri. Consequently, in this experience we see Turning the internal energy of the body into mechanical work. Note that the mechanical energy of Giri does not change in this experience - it is all the time equal to zero.

So, internal energy - This is such a body energy, due to which mechanical work can occur, while not causing the mechanical energy of this body.

The internal energy of any body depends on the set of reasons: the genus and state of its substance, mass and temperature of the body and others. All bodies have internal energy: large and small, hot and cold, solid, liquid and gaseous.

Internal energy can be used easily on the needs of a person only, figuratively speaking, hot and combustible substances and tel. These are oil, gas, coal, geothermal sources near volcanoes and so on. In addition, in the XX century, a person learned how to use the internal energy of the so-called radioactive substances. This, for example, uranium, plutonium and others.

Take a look at the right side of the scheme. In popular literature, thermal, chemical, electrical, nuclear (nuclear) and other types of energy are often mentioned. All of them, as a rule, are varieties of internal energy, since, due to them, mechanical work may be carried out, without causing the decrease in mechanical energy. We will consider the concept of internal energy in more detail with further study of physics.

Energy is a common measure of various forms of motion of matter. Accordingly, the forms of motion of matter distinguish between the types of energy - mechanical, electrical, chemical, etc. Any thermodynamic system in any condition has some reserve of energy, the existence of which was proven by R. Clausius (1850) and received the name of internal energy.

Internal energy (U) is the energy of all types of movement of microparticles that make up the system, and the energy of their interaction among themselves.

The internal energy is consisted of the energy of the translational, rotational and oscillatory movement of particles, the energy of intermolecular and intramolecular, intra-industrial and intracererial interactions, etc.

Energy of intramolecular interaction, i.e. The energy of the interaction of atoms in the molecule is often called chemical energy . Changing this energy takes place in chemical transformations.

For thermodynamic analysis, there is no need to know from which forms of motion of the matter there is an internal energy.

The supply of internal energy depends only on the state of the system. Consequently, the internal energy can be considered as one of their characteristics of this state on a par with such values \u200b\u200bas, pressure, temperature.

Each state of the system corresponds to a strictly defined value of each of its properties.

If the homogeneous system in the initial state has volume V 1, pressure P 1, temperature T 1, internal energy U 1, specific electrical conductivity æ 1, etc., and in the finite state, these properties are respectively equal to V 2, P 2, T 2, U 2, æ 2, etc., the change in each property when switching the system from the initial state to the final will be the same, regardless of how the system is moving from one state to another: the first, second or third (rice . 1.4).

Fig. 1.4 Independence of the properties of the system from the path of its transition

from the usual state to another

Those. (U 2 - u 1) i \u003d (u 2 - u 1) ii \u003d (u 2 - u 1) iii (1.4)

Where are the figures I, II, III, etc. Indicate the paths of the process. Therefore, if the system from the initial state (1) in the final (2) will switch to one path, and from the final at the beginning - on the other path, i.e. A circular process (cycle) is performed, the change in each properties of the system will be zero.

Thus, the change in the status function of the system does not depend on the path of the process, and depends only on the initial and end states of the system. The infinitely small change in the properties of the system is usually the differential sign D. For example, Du is an infinite small change in internal energy, etc.

Energy exchange form

In accordance with various forms of motion of matter and various types of energy, there are various forms of energy exchange (energy transmission) - forms of interaction. Thermodynamic examines two forms of energy exchange between the system and the environment. This is work and heat.

Work.The most visual form of energy exchange is a mechanical work corresponding to the mechanical form of motion of matter. It is produced when the body is moved under the action of mechanical strength. In accordance with other forms of movement of matter, other types of work are distinguished: electrical, chemical, etc. The work is a form of transmission of an ordered, organized movement, since when performing the body, the body particles move organized in one direction. For example, performing work when expanding gas. Gas molecules in the cylinder under the piston are in chaotic, disordered movement. When the gas begins to move the piston, that is, to make a mechanical work, an organized movement will be imposed on the erratic movement of gas molecules: all molecules receive some displacement in the direction of the movement of the piston. Electric work is also associated with the organized movement in a certain direction of charged particles of matter.

Since work is a measure of transmitted energy, its amount is measured in the same units as energy.

Heat. The shape of the energy exchange corresponding to the chaotic movement of microparticles constituting the system is called heat exchange, and the amount of energy transmitted under heat exchange is called heat.

The heat exchange is not associated with a change in the position of the bodies constituting the thermodynamic system, and consists in direct energy transmission by molecules of one body by the molecules of the other during their contact.

P redust the insulated vessel (system) separated into two parts with a heat-conducting partition AB (Fig. 1.5). Suppose that in both parts of the vessel is gas.

Fig. 1.5. To the concept of warmth

In the left half of the vessel, the temperature of the gas T 1, and in the right 2. If t 1\u003e t 2, then the average kinetic energy ( ) Gas molecules on the left side of the vessel, there will be more middle kinetic energy ( ) In the right half of the vessel.

As a result of continuous collisions of molecules about the partition in the left half of the vessel, the partition molecules are transmitted. The molecules of gas located in the right half of the vessel, facing the partition, will acquire some part of the energy from its molecules.

As a result of these clashes, the kinetic energy of molecules in the left half of the vessel will decrease, and in the right - increase; Temperatures T 1 and T 2 will be aligned.

Since the heat is a metering energy, its number is measured in the same units that energy. Thus, heat exchange and work are forms of energy exchange, and the amount of heat and the amount of operation are measures of the transmitted energy. The difference between them is that the heat is a form of transmission of the microphysical, disordered movement of particles (and, accordingly, the energy of this movement), and the work is the form of energy transfer of an ordered, organized motion of matter.

Sometimes they say: the heat (or work) is supplied or removed from the system, and it should be understood that it should be supplied and the heat and work is given, and energy, therefore, it is not necessary to use this kind of expressions as the "heat supply" or "heat contain".

As the shape of the energy exchange (forms of interaction) of the system with the environment, heat and work cannot be associated with any specific state of the system, they cannot be its properties, and, therefore, the functions of its condition. This means that if the system passes from the initial state (1) to the final (2) various paths, the heat and work will have different values \u200b\u200bfor different transition paths (Fig. 1.6)

The final amount of heat and work is denoted by Q and A, and infinitely small values \u200b\u200baccording to ΔQ and Δa. The values \u200b\u200bof ΔQ and Δa, in contrast to DU, are not a complete differential, because Q and A are not status functions.

When the process of the process is predetermined, work and heat will acquire properties of the system status functions, i.e. Their numerical values \u200b\u200bwill be determined only by the initial and end states of the system.

Internal energy- This is the energy of movement and interaction of molecules.

The kinetic energy of all molecules, of which the body consists, and the potential energy of their interaction make up internal body energy.

When the body is stopped, the mechanical movement ceases, but the disorderly (thermal) movement of its molecules is enhanced. Mechanical energy turns into the internal energy of the body

Internal energy Depends on the body temperature, the aggregate state of the substance and other factors.

The internal energy of the body does not depend on the mechanical movement of the body, or on the position of this body relative to other bodies.

If we consider the kinetic and potential energy of one molecule, then this is a very small value, because the mass of the molecule is small. Since the body contains a plurality of molecules, the internal energy of the body, equal to the amount of energies of all molecules, will be great.

Methods for changing internal energy

With increasing temperature, the internal energy of the body increases, as the average speed of movement of the molecules of this body increases. With a decrease in temperature, on the contrary, the internal energy of the body decreases.

Experience: If you warm the bottle with a rubber plug, then the plug will fly out after a while.

Thus, the internal energy of the body changes when the speed of movement of molecules changes.

Internal energy can be changed in two ways:

1) Making mechanical work. Internal energy increases, if work is done over the body, and decreases if the body makes work.

2) by heat transfer (thermal conductivity, convection, radiation). If the body gives heat, then the internal energy decreases, and if it takes heat, it increases.

Types of heat transfer. Experiments illustrating the types of heat transfer. Heat transfer in nature, technique, mechanics.

Heat transfer (heat transfer) - This is the process of changing internal energy, occurring without performing work.

1)

Thermal conductivity - The type of heat transfer, in which the energy is transmitted from one body to another when contacting or from one part to another. Different substances have different thermal conductivity. The thermal conductivity of the metals is large, in liquids - less, the gases are low. With thermal conductivity, the substance does not transfer.

2) Convection- The type of heat transfer, in which the energy is transferred by jets of gas and liquid. There are two types of convection: Natural and forced. There are no convection in solids, since their particles do not have great mobility. Many manifestations of convection can be found in the nature and life of a person. Convection also finds use in the technique.


3) Radiation - The type of heat transfer, in which the energy is transferred by electromagnetic waves. Bodies with a dark surface are better absorbed and emitted energy than bodies having a light surface. It is used in practice.

* With heat exchange, the number of removable heat is equal to the module of the number of the warmth obtained, or their amount is zero. This is called the level of heat balance.

The internal energy of any body is associated with the movement and state of particles (molecules, atoms) of the substance. If the full energy of the body is known, then the inner can be found, excluding from the full movement of the entire body as a macroscopic object, as well as the energy of the interaction of this body with potential fields.

Also, internal energy contains the energy of oscillations of molecules and the potential energy of intermolecular interaction. If we are talking about the perfect gas, then the main contribution to the internal energy gives the kinetic component. Complete internal energy is equal to the sum of the energies of individual particles.

As is known, the kinetic energy of the translational motion of the material point, which simulates the particle of the substance, strongly depends on the speed of its movement. It is also worth noting that the energy of oscillatory and rotational movements depends on their intensity.

Recomprive from the course of molecular physics formula for the internal energy of the ideal one-osomic gas. It is expressed through the sum of the kinetic components of all particles of gas, which can be averaged. Averaging in all particles leads to an explicit dependence of the internal energy on the body temperature, as well as on the number of degrees of freedom of particles.

In particular, for one-nominal ideal gas, whose particles have only three degrees of freedom of translational movement, internal energy turns out to be directly proportional to the three second works of the Boltzmann and Temperature.

Temperature dependence

So, the internal energy of the body actually displays the kinetic energy of the movement of particles. In order to understand what is the connection of this energy with the temperature, it is necessary to determine the physical meaning of the temperature value. If you heat the vessel filled with gas and having mobile walls, then its volume will increase. This suggests that the pressure inside has increased. Gas pressure is created by blowing particles on the vessel wall.

Once the pressure has increased, it means that the impact force increased, which indicates the growth rate of molecules. Thus, an increase in gas temperature led to an increase in the speed of movement of molecules. This is the essence of the temperature. Now it becomes clear that the increase in temperature leading to an increase in the speed of the particle movement entails an increase in the kinetic energy of the intramolecular movement, and therefore an increase in internal energy.

Internal energy - the most important condition for the existence and characteristics of all bodies alive and inanimate nature. In order to determine its importance in organizing life on our planet, remember the basic physical concepts of thermal speakers.

Macroscopic bodies consist of moving and interacting particles: molecules, atoms, ions. In turn, atoms and nuclei of atoms also consist of moving and interacting particles.

As you know, moving bodies have kinetic energy, therefore, particles (molecules, atoms, ions), of which the substance consists, also possess kinetic energy.

The interacting bodies have the energy of interaction, or potential energy. Since the particles of substance interact are among themselves, they possess potential energy.

Consequently, particles from which macroscopic bodies consist of kinetic and potential energy, their sum and there are internal energy macroscopic system.

Internal energy (U.) macroscopic system call the amount of kinetic energy (E. K) the movements of the components of its cha stitz (molecules, atoms, ions) and potential energy (E. N) their interacts:U \u003d.E K +.E P.

The unit of measuring internal energy is Joule (1 J).

The internal energy belongs to the energy of the movement and the interaction of particles that are part of atoms and the nuclei of the substance, however, in ME lectured physics, they deal with processes that occur with not too high temperatures and are not associated with the transformation of the substance. In these processes, intransimate and internal studary energy does not change.

Internal energy, as well as temperature, pressure and volume ( thermodynamic parameters), characterizes the state of the system. When the body change changes, the internal energy value changes.

As you know, the kinetic energy of the body is directly proportional to the square of its speed. Since molecules have different speeds and, therefore, different kinetic energies, their owl-checkiness is characterized by medium kinetic energy, which is directly proportional to the average square of the movement speed of the mole-kul:

Ėk. \u003d M 0 V̇ 2 / 2. Material from site.

Since the body temperature is directly proportional to the average kinetic energy of the components of its particles, the internal energy of the body depends on its temperature and the change in the internal energy can be judged by changing the body temperature.

The internal energy of the body depends on its aggregate state. So, it is more at the graduate steam than the water of the same mass at the same temperature. This is explained by the difference in the potential energy of the interaction of steam and water molecules.

Internal energy depends on the deformation of the body: it is more in the de-formated body than the undeformed.

It should be borne in mind that the internal energy of the body does not depend on its movement as a whole and on its position in space. Thus, the values \u200b\u200bof the internal energy at the ball lying on the floor and the raise on some height are the same with the same other conditions.

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