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Question: How do I describe the heat transfer by: conduction, convection and radiation? 


Answer: Conduction, convection and radiation are the three methods of heat transfer. Heat travels from one object to another. It moves from an object of higher temperature to one of lower temperature. When the two temperatures are the same, no more heat transfer will take place.

Conduction is the transfer of heat from molecules to adjoining molecules by collision.

Convection is the transfer of heat by the movement of liquids and gases.

Radiation is the transfer of energy in waves through space.

A radiator gives out some heat as conduction - if the central heating is on, the radiator will feel hot to the touch. Metals are good conductors because the electrons are free to move inside the metal. The heat moves from one particle to another in much the same way that a ball is passed from hand to hand along a line of players. The water in the radiator is heated by convection. Convection happens when the more energetic particles, which are hotter, move from the hotter region to a cooler region and take their heat energy with them. Warm particles rise. Warm water is not so heavy as cold water. Convection is a bit like a player running with a ball. The radiator gives out most of its heat as convection currents of warm rising air. Warm air is less heavy than cold air and can travel as convection currents through the room. The radiator also radiates some heat.

The warm particles of air can also travel by heat radiation. The window in your room allows heat to reach us from the sun by radiation. Heat radiation travels in straight lines at the speed of light. It will only travel through transparent media, like air, glass and water. Radiation is a bit like a player throwing a ball.




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