Thermodynamic temperature, also known as thermodynamic standard temperature, symbol T, unit K (Kelvin, referred to as open). As early as in 1787, the French physicist J.Charles discovered that at a certain pressure, when the temperature rises by 1°C, the increase in the volume of a certain volume of gas (expansion rate) is a constant value. The temperature is linear. The international practical temperature scale is based on a set of fixed points (such as balanced hydrogen triple point, equilibrium hydrogen boiling point, oxygen triple point, water triple point, tin solidification point, etc.) adopted by the international Reference thermometers (such as platinum resistance thermometers and platinum-10% rhodium/platinum thermocouples, etc.) and give the corresponding interpolation formula for temperature determination. Thermodynamic temperature One of the 7 basic quantities of the International System of Units (SI), the scale of the thermodynamic temperature scale, symbol T. According to the principle of thermodynamics, the thermodynamic temperature is measured and the international practical temperature scale is adopted. The thermodynamic temperature was formerly known as Absolute Temperature. The unit is "Kelvin", English is "Kelvin" for short "open", international code "K". Kelvin was named after the British physicist Lord Kelvin. With absolute zero (0K) as the minimum temperature, the temperature of the triple point of the specified water is 273.16K, which is defined as 1/273.16 of the thermodynamic temperature of the triple point of water. Celsius is a special name that is used instead of Celsius. The triple point temperature of water is 0.01 degrees Celsius. So the relationship between the thermodynamic temperature T and the temperature Celsius temperature T that people use is: T(K)=273.15+T(°C). The unit temperature (K) of the specified thermodynamic temperature is exactly the same as the average value in degrees Celsius (°C) of Celsius. Therefore, ΔTK = ΔT °C When the temperature difference and temperature interval are expressed, the values ​​of K and °C are the same. So many people often write 1K=1°C, which is an absolutely wrong example! Thermodynamic temperature Absolute temperatures mentioned in engineering thermodynamics are positive and negative temperatures above absolute zero. However, after the 1950s, in the study of nuclear magnetic resonance and laser effects, it was found that in the nuclear spin system and the laser system, particles only have two energy forms: ground state and excited state. At positive absolute temperatures, the number of excited particles is greater than the number of particles in the ground state. However, in nuclear spin systems and laser systems, the number of particles in the ground state exceeds the number of excited particles. According to Boltzmann's particle distribution function expression, if the number of ground state particles (atomic or molecular) is greater than the number of excited state particles, the absolute temperature should be negative, ie, a negative absolute temperature can occur. This is because according to Boltzmann's particle distribution function expression, when the absolute temperature is higher than infinity, the number of particles whose excited state particle number exceeds the ground state can be realized, and negative absolute temperature can occur. That is, the energy of the negative absolute temperature system is greater than the energy of the infinite absolute temperature, resulting in the negative absolute temperature being actually higher than the positive absolute temperature. The temperature in classical thermodynamics does not have the concept of the highest temperature, only the theoretical minimum temperature "absolute zero." The third law of thermodynamics states that "absolute zero" cannot be achieved through a limited number of steps. In statistical thermodynamics, temperature is given a new physical concept—an intensity-type thermodynamic quantity that describes the rate of change in the system with the degree of chaos (ie, entropy) of the system. This created a completely new theoretical field of “negative temperature zones for thermodynamicsâ€. In general, the environment we live in and the systems we study are all systems that have infinite quantum states. In such systems, the internal energy always increases with the increase in the degree of chaos. Therefore, there is no negative thermodynamic temperature. While a few systems with finite quantum states, such as laser-induced crystals, continue to increase the internal energy of the system until the degree of chaos in the system has not changed with changes in internal energy, it has reached an infinite temperature, and at this time, the internal energy of the system is further increased. That is, when the so-called "particle population reversal" is reached, the internal energy increases with the decrease of the degree of chaos. Therefore, the thermodynamic temperature at this time is a negative value! However, there is no classical algebraic relationship between the negative temperature and the positive temperature. The negative temperature is a temperature higher than the positive temperature. The concept of temperature scale extended by quantum statistical mechanics is: infinite quantum system: positive absolute zero degree "positive temperature" positive infinity temperature, finite quantum state system: positive absolute zero "positive temperature" positive infinity temperature = negative infinity temperature "negative temperature" negative Absolute zero. The positive and negative absolute zeros are the lower and upper limits of the thermodynamic temperature of a finite quantum state system, respectively, and cannot be achieved by a finite number of steps. The thermodynamic temperature Thermodynamic temperature, also known as thermodynamic standard temperature, symbol T, unit K (Kelvin, referred to as open). As early as in 1787, the French physicist J.Charles discovered that at a certain pressure, when the temperature rises by 1°C, the increase in the volume of a certain volume of gas (expansion rate) is a constant value. The temperature is linear. The initial experiments showed that the fixed value was 1/269 of the volume of the gas at 0°C. Later, it was corrected by many people through decades of experiments. Among them, especially in 1802, the French Guy Lussac (JLGay-Lussac) The work finally determined the value of 1/273.15. The relationship between the above gas volume and temperature is expressed by the following formula: V=V0(1+T/273.15)=V0(T+273.15)/273.15 where V is the volume of gas at the Celsius temperature T/C. If we define T+273.15≡T (therefore 0°C+273.15=T0), the above relation can be expressed by a simpler formula: V/T=V0/T0. Further, V1/T1=V0/T0,V2 /T2=V0/T0,..., naturally there is V1/T1=V2/T2, that is, a certain amount of gas at any temperature. When the pressure is constant, the volume V of the gas is inversely proportional to the temperature represented by T as a temperature scale. This is called Charlie Gay Lusack's law. In fact this relationship only applies to ideal gases. To this end, people first referred to T as the ideal gas temperature (temperature scale), also called the absolute temperature (temperature scale). After the formation of thermodynamics, the temperature scale was found to have a deeper physical meaning. In particular, Claosius and Kelvin demonstrated that absolute zero was not attainable, they renamed the thermodynamic temperature (temperature scale), and used Kelvin's first letter. K is its unit. The temperature of an object is a macroscopic manifestation of the intense degree of motion (hot motion) of a large number of particles constituting an object. For example, the relationship between the average kinetic energy Ek of a large number of molecules of a gas composed of monoatomic molecules and its temperature T is deduced from the statistical thermodynamic theory as: E(-)K=3/2kT where K=1.391×10-23 J/K. The Boltzmann constant is equal to the ratio of the gas constant R to the Avogadro constant N0. 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