Transmission of heat

A) Definition : heat is a form of energy. it measured in calories and B.T.U(Fahrenheit = 1 b.t.u )

B) Units:
                  Calory : the amount of heat require to raise 1 degree temp of 1 gram  water is called 1 calory.

                  B.T.U  :  Energy require to raise 1 degree temp of 1 pound water . (1 B.T.U = 1 Fahrenheit )

C) Specific heat : energy required to raise 1 degree of any 1 gm substance.
D) Latent heat :  1. Latent heat of vaporization.
                           2. Latent heat of freezing


Latent heat of vaporization : amount of heat required to convert 1 gm of  water in to vapor is called latent heat of vaporization of water.(at 100 degree , 540 calories/gm needed for water)

Latent heat of freezing: amount of heat required to convert 1 gm of  water in to solid ice is called latent heat of vaporization of water.(at 0 degree , 80 calories/gm needed to convert water to ice)

 

TRANSMISSION OF HEAT

 1) Conduction

       The heat travels through the molecule of substance without movement of molecule themselves.(molecule doesn’t travels.)

 

 

 

 

 

2) Convection :

          When the fluid (liquid and gas) heated the expands so the heated molecules become lighter and moves upward and cold molecules takes place . this process continues. 
 

 

 

3) Radiation :

             In this way heat travels without any medium. it does not heat the medium approximately. heat travels in a straight line.
e g : heat from sun comes without any medium (zero atmosphere) to the earth by radiation.