In our everyday life, we may observe that a cup of tea or coffee kept in the room cools down and its temperature matches that of room temperature, why? How the bucket of hot water cools down in the bathroom after 30 minutes of not using it? The cooling of tea and hot water in the bucket takes place due to the mechanism of heat transfer. Hot bodies or objects get cool down since the heat content of an object does not stay constant, heat transfers from a hotter body to the cooler body.
Mechanism of CONDUCTION
When we go for a long drive in a car; you stop at someplace and open Bonnet or Hood of the car to let it cool down, why do we do that? How the bonnet gets hot? Why you can’t walk barefoot on the tar in summer?
- Why a teacup or rice bowl gets hot when tea or rice poured and cooked in the cups and bowls?
- Why your shirt or skirt becomes hot when you are ironing it?
- Why spoon becomes hot when you put it in the hot rice bowl?
The bonnet, barefoot; spoons and shirts/skirts get hot due to the heat transmitted into them. This process of heat transmission is called Conduction. Here the molecules of objects vibrate their near molecules to transfer the heat from one end of the object to another end.
Process of CONVECTION
How does the radiator in the room heat the air in the room to keep us warm?
- How does our ice cream or frozen food melts or thaws?
- How the hot air balloon can fly in the air or space?
- How does hot water boil?
The hot water molecules raise as they get heat and the cool water molecules rush down to replace them making a circular motion called Convection Currents. Here the heat is transferred by the movement of fluid or gas between different temperatures. This process is called convection. The radiator, melting of ice cream, and hot balloon flying is just work of convection currents.
How RADIATION works?
When you stand in the corridor for the morning assembly in summer, why your black shoe starts getting hot?
- How campfire in winter warms us up?
- How do remote controls work?
The heating up of black shoe, warmth by a campfire and remote controls work based on Radiation they emit to heat objects. The radiation like either of Conduction and Convection needs no medium to transfer heat. They transfer in waves or particles through space or material medium. Other than this which emits heat through radiation are – Bulbs, X-ray or CT scan; nuclear power production and weapons used for security.
Where do we apply our ‘HEAT TRANSFER’ knowledge?
Without the knowledge and understanding of the mechanism of Heat transfer, the invention of solar technologies like – Solar heaters, Cookers and solar electricity would be impossible. The designing of power systems like – Thermal power station, Nuclear energy and weapon production; use of geothermal energy and air/ground sourced heat pumps need the knowledge of heat transfer to control the heat in the systems. To get a deep understanding of Modes of heat transfer, we can use different teaching and learning materials, like – Models, charts; visual aids and other hands-on learning materials.
Check our hands-on learning activity video glimpses to know more about the ‘Heat – Modes of Transfer’ and for many more interesting activities.