Convection

In this method a hot body flows to a colder body. As a result the colder body gets hot. Since only liquids and gases can flow, therefore this mechanism is restricted to liquids and gases. Let’s consider some examples:

In the illustration shown here we are demonstrating how water boils. Notice that we heat the base of the water container. Therefore, water at the base gets hot. The density of the hot water is less than that of the cold water. Therefore, the hot water rises toward the top. As this happens, the rising hot water comes in contact with the colder water and heats it up. This is an example of heat transfer by convection.

The steam leaves the container at the top and begins to rise up in the atmosphere. As it rises up, it heats the air it comes in contact with. This is another example of heat transfer by convection.