Imagine a cup of hot coffee and bowl of cold ice cream placed on a table. After some time, you may find that the coffee has got cold and the ice cream has got warm (as a result of which it starts melting). This happens because of the process of heat transfer with the air inside the room.
The three basic processes of heat transfer are conduction, convection and radiation.
Conduction is what we experience when we hold a metallic spoon over fire. Slowly the other end of the spoon that we hold gets hot. This is ‘conduction’ caused by rapid movement of atoms as they get warmer and warmer.
Convection is the dominant form of heat transfer in liquids and gases. When a hot cup of tea is placed on a table, it heats up a layer of air surrounding the cup. The hot air rises, then the cold air takes its place. This cold air again gets heated up and the cycle repeats and thus coffee cools down. That is why we blow air over hot liquids in order to cool them down.
Rapid movement of atoms not only produces heat but also some vibrations. You may be surprised to know that these vibrations cause infrared radiations. These radiations when absorbed results in atomic motion which in turn causes friction. Friction releases heat rising the temperature further. For example, the heat that comes from the concrete walls even after the sun has set is an example of infrared radiation.
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