Condution, Convection & Radiation

Revision for Conduction, Convection & Radiation.

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Conduction

Conduction is about when heat is transferred through a solid, the heat is passed on by vibrations in the molecules. The vibrations get bigger when the solid has more energy (when it is being heated).

Metals are better conductors than wood or other non-metals and this is because the heat is carried by free electrons that can carry energy around the metal and give the heat to other electrons and ions.

In conduction the heat is passed on by vibrations in a solid.

A good conductor of heat is Copper and a bad conductor is Wood (good insulator).

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Convection

Convection is about when a gas or liquid moves and carries heat with it, when the gas or liquid is heated it expands. This means that it will become less dense than the colder liquid or gas around it. Because of this the warmer liquid or gas will try to float over the cold liquid or gas, and this is the reason why warm air rises.

This is called a Convection Current and this is how the heat from the radiators reaches us.

In convection the heat is passed on by the the liquid or gas expanding, rising and taking the heat with it.

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Radiation

Radiation is when heat moves around the electromagnetic waves like light does, any hot object will give out (Emit) heat radiation and the hotter it is , the more radiation is given out. This type of radiation is called Infra-Red and too much of it will cause sunburn. Dark, matt colours like black will adsorb and give out the most infra-red radiation and light, shiny coulours like wihte will reflect it.

The main difference with radiation is that Conduction and Convection can only happen in solids, liquids or gases, whereas radiation will happen in an empt space (Vacuum). This is the reason we get heat from the sun.

Things that use colour radiation are Solar Panels, Pipes, Houses in hot Countries and a Kettle.

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