Heat transfers from one point to another due to the temperature difference between them. The three mechanisms by which heat can be transferred are Conduction. Convection and radiation.
Conduction takes place in a material or between two materials in Contact. Convection depends on the motion of molecules and so the motion of molecules and so the motion of mass from one region to another region of space. Radiation is the heat transfer between the materials by the electromagnetic waves without any medium between them.
It is the process in which heat is transferred through a material without the movement of the material. In conduction, heat is carried by means of collision between rapidly vibrating atoms( or molecules) at the hot end of the material and slower vibrating atoms at the cold end. Some of the kinetic energy of fast vibrating atoms passes to the slow atoms and the result of successive collisions is a flow of heat through the body of material. For example, when one end of a material
For example, when one end of a material is heated, the atoms at hotter end vibrate with greater amplitude and have more kinetic energy than the neighbouring atoms at cooler region and these atoms give up some energy to the neighbouring atoms at cooler region and these atoms give up some energy to the neighbouring atoms in cooler region. These atoms also collide with other neighbouring atoms passing the energy and this takes place throughout the material. so the atoms do not move from one region of the material to another but their energy transfers. Solids, liquids and gases all conduct heat, but conduction is poorest in gases as their molecules are relatively far apart and interact less frequently than in solids and liquids.
A simple mechanism occurs in metals for the conduction of heat. However, metals contain electrons moving randomly throughout the material and these electrons can carry energy from the hotter to the cooler regions of the materials also. The free electrons are also responsible for the excellent electrical conductivity that metals have.
Application of conduction
i) in winter, iron chairs appear to be cooler than wooden chairs:
==> Iron is good conductor of heat. When we touch them, they absorb the heat from our body. Since our body loses heat, we feel cold. On the other hand, wood is a bad conductor of heat and so there is no transfer of heat from our body to the wooden chair. Hence wooden chairs appear cooler than iron chairs.
ii)Ice is packed in sawdust:
==> Sawdust from the wood is a bad conductor and air trapped in it also prevents a transfer of heat from the surroundings to the ice. Hence ice does not melt.
iii)Woolen clothes are warm because they have fine pores filled with air:
==> Wool and air are a bad conductor of heat. So, woollen clothes prevent the heat conduction from the body to the surroundings and hence keep the body warming in the winter.
iv)Eskimos make double walled houses of the blocks of ice:
==> The air enclosed between the double walls is a bad conductor of heat. It reduces the transmission of heat from the house to the cold surroundings. Therefore, the people living in these houses feel warmer.
Also read: Difference between conduction and convection