As we know that heat flows from the body at higher temperature to the body at a lower temperature, this flow of heat is known as transfer of heat from one place to another. For that, we have to learn about conduction, convection, and radiation.
Conduction, Convection, and Radiation
In solids, heat is transmitted from higher temperature to lower temperature without actual movements of the particles. This mode of transmission of heat is called conduction, e.g., when one of a metallic rod is heated, its other end becomes hot
The mode of transfer of heat from one part of the medium to another part by the actual movement of the heated particles of the medium is called convection. In liquid and gases, transmission of heat takes place by convection process.
Application of convection
Different applications of convection are as follows
i) Formation of Sea Breeze Die to solar heat, the land, and seawater get heated. The ground is heated more quickly than water because water has greater specific heat. The air in contact with the ground is heated due to conduction, so it expands and becomes lighter than the surrounding cooler air. So, the warm air rises resulting in air currents, the cooler air from above moves down fill space. This creates the sea breeze near a large quantity of sea water. In this way, a thermal convection cycle is set up which transfers away from the ground.
ii) Formation of Trade Wind The steady surface wind on the earth blowing from north-east towards equator, is called trade wind.
Solar heat reaching the equatorial region is higher than that of polar region. So, the air in contact with equator gets heated, becomes lighter and moves towards pole and the cooler air at poles moves towards the equator. So. convection currents set up from equator towards poles. The rotation of earth modifies this current, due to this the air closed to the equator has high speed of 1600 km/h towards east and zero at the poles.
iii) Ventilation Convection process is an important part in the ventilation of rooms. When the fire is lighted, the air in the chimney is warmed. It becomes less dense than the air in the room. The warm air is forced out by the cold fresh air which enters the room through the inlet and gaps in the doors and the window. Thus, draughts of air are formed in the room which help to keep the fire supplied with oxygen.
The mode of transfer of heat from one body to another without any actual movement the particles involved and without heating, the intervening medium is called radiation. For radiation, there is no need of any medium because it is of electromagnetic nature.