Thermal Processes

Modes of Heat Transfer: Conduction, Convection, and Radiation

Conduction

• In this mode of transfer of heat, particle to particle transfer of heat takes place, through interatomic collisions.
• It is the slowest mode of transfer of heat.
• Metals are good conductor of heat.
• With increase in specific heat capacity, the rate of conduction of heat through the material decreases.

• Same amount of heat is supplied to all of the above metal rods. After time “t”
• Conduction of 1 > 2 > 3 > 4.
• For fair test —-
  • Numbers of balls should be the same.
  • Amount of heat supplied to each rod should be same.
  • Same size of wax balls.

Convection

• In this process particles carry energy from one place to another.
• Convection occurs in a fluid due to density differences in the medium.

Radiation

• It is a transfer of thermal energy in the form of electromagnetic radiation in the infrared frequency range.
• It does not need material medium to travel.
• It is the fastest mode of transfer of heat. It travels at the speed of light in vacuum.
• The rate of absorption and emission of radiation increases with the roughness of the surface.
• Rate of emission of radiation from a dull, black surface is greater than white, shiny surface.

The reflection of radiation from a shiny, white surface is the greatest.