Question

How many ways can you see that heat can transfer from the inside to the outside of your room on a cold day? List at least three and describe in detail how heat moves through the different kinds of materials (glass, brick, wood, insulation, etc.)—by conduction, convection or radiation. Which process do you suppose dominates?

Answer 1

There are many ways in which heat tranfer may occur like :

Assume that the temperature outside is lower than the temperature inside the room

1. Heat transfer can occur through air via window. The relatively hot air inside the room will have greater energy than the air outside. so, the hot air from the window of the room will go outside and outside air may come inside. This will cause heat transfer and change in temperature of the room.

2. Talking about the medium heat can only transfer through the materials which are good conductors of heat. Suppose we have a large room having large number of closed glass windows. Now since the air cannot pass through the closed window even then heat transfer may occur. Initially if the temperature inside the room is higher than the surrounding then the glasses will become from inside and it will transfer this energy (not completely) to the outside environment (air). Thus lowering the temperature of room. Note that if we take wood or insulated material then heat cannot transfer through it.

3. The atmosphere gets heated by the radiation coming from the sun. Now taking the example of room (low temperature than surrounding here) heat may transfer to the room by any of the above methods.

Now, saying formally the method of heat transfer in the first part is called convection, since here heat transfer occurs through the bulk movement of molecules

In the next part the method of heat transfer is called conduction, since here heat transfer occur though collision of particles inside the material.

In the last part, the method is called radiation, since here transfer of heat occurs through the transfer of energy in the form of waves or particles through space.

Heat is transferred usually in the combination of the three process. But radiation may be the dominant factor because we all are surrounded by radiations like from light bulbs, sun etc.