Thermodynamic temperature

When pressure of real gas is decreased, it act as an ideal gas. Ideal gas has relationship between pressure p, volume V, temperature T is

pV/T = constant

T is thermodynamic temperature of the body, and measured in Kelvin (ºK)

One kelvin is the fraction of 1/273.16 of the

thermodynamic temperature of the triple point of water. 

To avoid complications and confusion between empirical centigrade scale based on experiments with real gases and constant-volume gas thermometer scale, a new scale, the Celsius scale was defined by international agreement which is 

Unit of Celsius scale, which is degree Celsius (℃)
has same scale as thermodynamic scale, which is Kelvin(ºK).

Thus, Temperature θ ℃= T/K - 273.15 or T/K = θ ℃ + 273.15

To avoid confusion of absolute zero, which is 273.16, and number used in this equation, 273.15, and for various purposes, it is sufficient to work with the number 273

 

Thermal Physics

A level Thermal Physics

(based on the book 'International A/AS level physics endorsed by Cambridge')

Temperature 

Properties of temperature

A temperature (n) is an objective comparative measure of hot or cold (Wikipedia)

• Temperature is transferred from high temperature to the low temperature. This is caused by vibration of the atoms of the metal. Atoms passes on some of its vibration to its neighbor. In this spreading process, energy is lost to other atoms until it is evenly spread. The state when it is evenly spread Thermal equilibrium.
• Temperature can expand volume of most materials.
• Temperature can increase resistance in electrical moments
• Measures how hot a body is not how much heat energy it has.
• 0ºC  273ºK / -273ºK  0ºC

Temperature scales

Thermometer

Thermometer is an instrument for measuring temperature.

• Uses thermometric property
• measured in degrees (Kelvin as ºK or degree Celsius as ºC)

Thermometric scale

  Thermometric scale is formed from the point where the substance changes its state (e.g. solid to liquid, liquid to gas). This temperature is called fixed point. Dividing the value of the thermometric property at two fixed point into equal steps (or degrees), thermometric scale of that thermometer is formed.

  Theoretically, setting fixed point at melting point of ice and boiling point of water, and dividing it by 100 equal steps (in this case, degrees), empirical centigrade scale of this thermometer is formed. If we call property at ice point P_i and property at boiling point P_s, For unknown temperature at θ, property of point θ can be calculated this equation.