Question

Give one example each of natural convection and forced convection.

Answer 1

Explain the difference between natural convection and forced convection. As the name suggests, the forced convection is obviously induced convection by the external means.The forced convection is the induced convection by the means of external sources like fan.

Complete answer:
To answer this question, we have to understand the meaning of convection. We observe when we place the cup of hot coffee on the desk, after some time, the desk also becomes hot. There is a transfer of heat from hot coffee to the desk.
Convection: It is the transfer of heat with the fluid or gas when there is temperature difference between the layers of the fluid. Therefore, a less dense layer of fluid (High temperature) rises upward and the low density fluid replaces it. This process is known as convection.
We know that there are two types of convection: Natural convection and forced convection.The natural convection involves movement of the layers of fluid or gas, when there is difference in the densities of the layers. It is not caused by the external source. We see various examples of natural convection in day today life. One of them is a land breeze. It happens during the daytime when the sun is up and heats both land and sea surface. Since the land surface heats up more rapidly than the sea surface, the air above the land surface becomes less dense. This generates a pressure gradient and the air above the land surface moves towards the sea. This movement of air, we call it land breeze.The forced convection is the induced convection by the means of external sources like fan, exhaust fan and pumps. In summer, when we sweat, we turn on the fans. The fan moves the warm air and replaces it with cold air. Also, a water heater is an example of forced convection.

Note: Do not get confused between conduction and convection. The conduction is also the transfer of heat due to temperature gradient but it is not due to density gradient. The convection occurs because there is movement of layers of the same fluid or air due to their relative difference in densities.