Convection is the transfer of thermal energy from one place to another by means of bulk fluid movement in the material medium.
In fluids, thermal energy transfer is mainly through thermal convection. In solids, since its substance cannot flow, there can be no thermal convection.
In convection, the movement occurs as a result of gravity. The hot part of the fluid expands, becomes less dense and rises. It is displaced by the colder, denser part of the fluid, which in turn is heated up. This fluid movement or convection current allows heat to be transported.
Applications Of Convection:
In a refrigerator, convection is used to circulate cold air around the food. Air is cooled by freezer compartment at the top of refrigerator. As it sinks, it is replaced by warmer air rising from below. The circulating air carries away heat energy from all the food in the fridge.