Microscopic explanation of the second law of thermodynamics in high school physics

There is nothing logically wrong with your statement, the Kelvin interpretation of the second law of thermodynamics is that heat cannot be absorbed from a single heat source and converted all of it into work without other effects, while your statement is that there are other effects, so there is nothing wrong (just like an ideal gas, pv=nrt absorption temperature, t rises, if p does not change, then v increases, and on the way to outward expansion, it must do work outward). ）

But when it comes to the topic, it is impossible to convert all the internal energy into mechanical energy, and if the internal energy is to be converted into mechanical energy, then there must be other effects, because the ideal gas does not exist...

In fact, these high school questions are very tangled and nonsense, and the explanations given are generally what the topic needs, so they are explained.

It is recommended that you choose according to other options, in general.

The upstairs explanation is that the entropy must be constantly increasing, and there is a way to understand what you mean3

It's like you can pour a bottle of water into the ocean, but you can't pour the water into the bottle (not because the bottle doesn't fit, of course). The internal energy of the system is proportional to the temperature t, and if you want to completely convert the internal energy of the system into mechanical energy, first you have to find a way to reduce its temperature to absolute zero (of course, absolute zero cannot be reached), and secondly, you have to completely convert the energy released by the system into mechanical energy in this process. Neither of these processes is achievable.

The internal energy of an object includes the kinetic energy of the molecule and the potential energy, and the molecule is in irregular and never-ending motion, so this part of the energy cannot be converted, that is, the internal energy cannot be completely converted into mechanical energy.

The microscopic explanation of the second law of thermodynamics is as follows:

The molecules in both the high-temperature object and the low-temperature object are doing irregular thermal motion, but the average rate of molecular thermal motion in the high-temperature object is greater than that of the low-temperature object, so in the collision process between the molecules of the high-temperature object and the molecule of the low-temperature object, the intensity of the molecular motion of the low-temperature object will gradually intensify, that is, the temperature of the low-temperature object increases;

And the intensity of the molecular motion of the hot object will slow down, that is, the temperature of the hot object will decrease, so from the perspective of macroscopic thermal phenomena, the heat transfer is directional, and it is always transferred from the hot object to the low temperature object.

In other words, we distinguish two objects according to the temperature of the initial state, and the temperature of the two objects in the final state is the same everywhere and cannot be distinguished, so we say that the disorder degree of the system has increased.

In the same way, it can be seen that in the process of increasing the energy in the system by doing work, the natural process is the process of the transformation of a large number of molecules from an ordered state of motion to a state of disordered motion.

Second law of thermodynamics

One of the fundamental laws of thermodynamics, expressed by Clausius, states that heat cannot be spontaneously transferred from a cold object to a high temperature. Kelvin is stated as:

It is not possible to take heat from a single heat source and convert it completely into useful work without any other effects. Entropy increase principle: The micro-increment of entropy in an irreversible thermal process is always greater than zero.

In natural processes, the total degree of chaos (i.e., "entropy") of an isolated system does not decrease.

The phenomenon of heat involves the random movement of a large number of particles. Random movement is not complete"Random"of these, the thermal phenomenon to meet a certain amount"Regularity"。The second law is not the total sign of experience"Phenomenology"Description.

The physical nature of the second law has to be passed"Microscopic"or the description of the clan argument.

Work to heat: mechanical energy is converted into heat energy, and microscopically the orderly movement of a large number of molecules is transformed into disordered motion.

Heat transfer: The disordered movement of a large number of molecules increases due to heat transfer.

Adiabatic free expansion of gases: the molecular motion state is more disordered.

Answer] :d All spontaneous processes of manuscript thinking are irreversible. a, work can be converted into heat in its entirety, but heat cannot be converted into motion without causing any other change (external environment); Item b, one of the views of the second law of thermodynamics:

It is impossible for heat to be transferred spontaneously and unconsciously from a cold object to a hot object; C, the state in which the reverse process cannot be repeated without causing other changes is called an irreversible process.

Classifier: Education Academic Exam >> College Entrance Examination.

Problem description: The second law of thermodynamics says that it is not possible to absorb heat from a single heat source and convert it into mechanical work without causing other changes. If other changes are caused, can the heat absorbed be completely converted into mechanical work?

There is a question that is like this, d: mechanical energy can be completely converted into internal energy. Internal energy may also be completely turned into mechanical work.

Analysis: Even if other changes are caused, the heat absorbed from a single heat source cannot be converted into mechanical energy.

d.Mechanical energy can be completely converted into internal energy. It is also wrong to convert internal energy into mechanical work completely.

Good luck!

a.Energy can only be converted, not increased or eliminated.

b.Energy is directional in the conversion.

c.Energy can only increase this fierce age or turn the forest to change and cannot be destroyed.

d.Energy is non-directional in the conversion.

Correct Answer: Energy is directional in the transformation.

Use the method of counter-evidence. If two absolute ** can intersect, plus an isotherm can form a loop (closed curve). This cycle only absorbs heat from a single heat source in an isothermal process and then does work externally, which clearly violates the second law of thermodynamics.

Therefore, it is absolutely impossible for two to intersect.