How to understand the consistency of the two formulations of the second law of thermodynamics? 5

What is the second law of thermodynamics.

This is what the two sentences say about the transfer of heat from a low-temperature object to a high-temperature object, which requires the workmanship of other substances.

All in all, it's entropy! Looking at the formula for entropy change, it is clear.

The two formulations of the second law of thermodynamics are as follows:

1. Two expressions of the second law of thermodynamics.

1. The first is Clausius formulation: it is impossible to transfer heat from a cold object to a high temperature object without causing other changes.

2. The second is Kelvin's formulation: it is impossible to make a heat engine with a cyclic action, take heat from a single heat source, and make it completely become work without causing other changes. The Kelvin formulation can also be expressed as the second type of perpetual motion machine is impossible to achieve.

2. In addition, the second law of thermodynamics can also be expressed as the principle of increasing entropy: the entropy of an isolated system never decreases automatically, and the entropy does not change in the reversible process and increases in the irreversible process.

3. In a microscopic statistical sense, thermal motion is the irregular movement of a large number of molecules. Irregular motion has a very small chance of becoming regular, while regular motion has a high chance of becoming irregular. The internal spontaneous process of an isolated system that is not affected by the outside world always proceeds from a state with a small probability to a state with a high probability, so it can be seen that heat cannot be spontaneously successful.

4. Explanation of the second law of thermodynamics.

1. Heat can be spontaneously transferred from a hotter object to a colder object, but it is not possible to spontaneously transfer from a colder object to a hotter object (Clausius formulation); It can also be expressed as follows: the result of the friction of two objects turning work into heat, but it is impossible to convert this frictional heat back into work without other effects.

2. For thermal processes such as diffusion, osmosis, mixing, combustion, electric heat and hysteresis, although their inverse processes still conform to the first law of thermodynamics, they cannot occur spontaneously. The first law of thermodynamics does not address the direction, conditions, and limits of energy conversion, which are precisely dictated by the second law of thermodynamics.

Differences: 1. The rules are different.

The first law is the rule that describes the existence of energy, and the second law is the rule that describes the energy transformation of the potato crack.

2. The interpretation of energy is different.

The first law is the conservation of energy, and energy cannot be self-generating or self-extinguishing, but is transformed in different forms. The second law states that it is impossible for heat energy to be spontaneously transferred from a low-temperature object to a high-temperature object, and that heat is converted into work without other effects.

3. Different application methods.

The first law states that there is no increase or loss of energy in any thermodynamic process, and there are no restrictions on natural processes, while the second law of thermodynamics addresses which processes can be counted to occur.

Connection: The two suggest the laws followed in the thermodynamic process from different perspectives, which are independent of each other and complement each other, and together constitute the theoretical basis of thermodynamic knowledge.

The second law of thermodynamics.

The second law of thermodynamics is expressed in several ways:

Clausius stated:

Heat can be spontaneously transferred from a hotter object to a cooler object, but it is not possible to spontaneously transfer from a colder object to a hotter object;

Kelvin-Planck formulates:

It is not possible to draw heat from a single heat source and turn that heat into work without other effects. Entropy Formulation:

Entropy in an isolated system does not always decrease over time. Relationship:

Each formulation of the second law of thermodynamics reveals the directionality of macroscopic processes in which a large number of molecules participate, and makes people realize that macroscopic processes involving thermal phenomena that occur in nature are directional. Micro significance.

All natural processes always proceed in the direction of increasing disorder in the thermal motion of molecules.

The second type of perpetual motion machine (which cannot be made).

A heat engine that absorbs heat only from a single heat source, turning it completely into useful work without causing other changes.

The second type of perpetual motion machine violates the second law of thermodynamics.