The first law of thermodynamics is the conservation law of different forms of energy in the process of transmission and transformation, and the expression is q = △ u+W. Expression: Heat can be transferred from one object to another, and can also be converted with mechanical energy or other energy, but the total value of energy remains unchanged during the conversion process.

The second law of thermodynamics, one of the basic laws of thermodynamics, is expressed as: it is impossible to transfer heat from a low-temperature object to a high-temperature object without other effects, or it is impossible to take heat from a single heat source and completely convert it into useful work without other effects, or the slight increment of entropy is always greater than zero in the irreversible thermodynamic process. Also known as the law of entropy increase, it shows that the total chaos of an isolated system (that is, "entropy") will not decrease in the natural process.

The first law of thermodynamics describes the law of energy conservation, that is, the perpetual motion machine of the first kind cannot be established.

The second law of thermodynamics describes the law of energy conversion, that is, the second kind of perpetual motion machine cannot be established.