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Conduction, Convection and Radiation: WRP_Physics_Avantika - Coggle Diagram
Conduction, Convection and Radiation: WRP_Physics_Avantika
Conduction:
Conduction is the flow of thermal energy (heat) through matter from places of higher temperature to places of lower temperature without movement of the matter as a whole.
Conduction mainly occurs in solids. One of the best thermal conductors is Copper. Insulators include glass and wood.
Liquids and gases also conduct heat but only very slowly. Water is a very poor conductor, as shown in Figure 23.3. The water at the top of the tube can be boiled before the ice at the bottom melts.
Convection:
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When the heat is provided, the volume of particles increases and thus their density decreases. These particles move above and the denser ones move below. Convection currents are set up.
Convection also occurs in gases. E.g. During daytime: Cool air from sea to land and during nightime: Cool air from land to sea
Air coolers are installed at the top of the room: This is because once the top air is cooled, it can sink down and the warmer one can rise which can be cooled again.
Room heaters are installed at the bottom of the room: This is because once the bottom air is warmed, it can rise and the cool air from the above can sink. Convection currents are set up and the whole room is warmed.
In fridges, cool air sinks below the freezer compartment. This sets up convectional currents and cools all of the food in the fridge.
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Absorbers, Emitters and Reflectors:
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Silver bodies are worst emitters and absorbers, but the best reflectors.
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In hot, sunny countries houses are painted white to reflect the light & keep them cool.