BASICS OF TEMPERATURE 

       In a simple language, temperature said to be

  •  Degree of hotness and coldness of body or environment       
  • The intensity of heat in the substance with reference to some standard value.
  • The transfer of heat energy from one substance to another is also measured in degree.
Temperature conversion table  :
To convert from
To
Formula
 Degree Celsius
Degree Fahrenheit
(C*9/5)+32
 Degree Celsius
Kelvin
(C+273.15)
Degree Fahrenheit
Degree Celsius
(F-32)*5/9
Degree Fahrenheit
Degree Rankin
(F+459.69)



Basic fix points :

  • Boiling point: the temperature of which  substance changes from liquid to gas
  • Freezing point: the temperature of which  substance changes from liquid to solid
  • Triple point:  a particular temperature and pressure of which three different phases of one substance exist in one equilibrium point. According to the Gibbs phase rule, the three-phase situation in component leaves it with no degree of freedom.
  • Absolute zero: the temperature of which molecular  motion completely ceases


Important laws in temperature :

  1. Seebeck effect
  2. Thermoelectric effect
  3. Thompson effect
  4. Peltier effect
  5. Law of homogeneous material
  6. Law of intermediate metal
  7. Law of intermediate temperature
  8. Seebeck Effect

The Seebeck effect 

  • Temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between them.

  • The Seebeck effect is the conversion of I4 differences directly into electricity.

  • In general, the Seebeck effect is described locally by the creation of an electromotive field

Peltier Effect

  • The Peltier effect is a temperature difference created by applying a voltage between two electrodes connected to a sample of semiconductor material. 

  • This phenomenon can be useful when it is necessary to transfer heat from one medium to another on a small scale.

  • The Peltier heat generated at the junction per unit time. 

  • Note that the total heat generated at the junction is not determined by the Peltier effect alone. as it may also be influenced by Joule heating and thermal gradient effects.

Thomson Effect

  • Thermoelectric couples: Consist of positive and negative elements connected electrically in series and parallel in heat flow.

  • Thomson Effect: The Thomson effect describes the heating or cooling of a current-carrying conductor with a temperature gradient.

  • Consider a conductor which is subject to the longitudinal temperature gradient and also to the potential difference such that there is a flow of current and heat in the conductor. The Thomson effect describes the mechanism that a current flowing in a wire in which a temperature gradient is present shows a heat exchange with its environment

Laws of Thermoelectricity :


A thermoelectric current cannot be sustained in a single homogenous material by the application of heat alone, regardless of how much it might vary in cross-section.


  • Law of Intermediate Material: The algebraic sum of thermoelectric forces in a circuit composed of any number of dissimilar materials is Zero if all of the circuit is at the same temperature.

  • Law of Successive or Intermediate Temperature: If two dissimilar homogeneous materials produce thermal (emf), when the junctions are T and T, and produce thermal (emf), when the junction is at 1, and T, the emf generated when the junction is at temperature T, and T, will be (emf), + (emf)

  • Law of Intermediate Material:  The algebraic sum of thermoelectric forces in-circuit composed of any number of dissimilar materials is Zero if all of the circuit is at the same temperature.

  • Law of Successive or Intermediate Temperature: If two dissimilar homogeneous materials produce thermal (emf), when the junctions are T and T, and produce thermal (emf), when the junction is at 1, and T, the emf generated when the junction is at temperature T, and T, will be (emf), + (emf)