World Builders™                                                                  Session Three  --  Meteorology             

                      
          Heat Transfer     

                          

Heat is transfered by three processes:  conduction, convection, and radiation.

     Heat flows from the heat source to cooler bodies. Heat is transferred by three processes: Conduction, Convection, and Radiation.

Conduction:

When heat is conducted, it is led from the heat source by travelling along a physical object.

Here two of Dr Viau's students are learning about conduction.

The young woman in the pink dress was using a straightened out coat hanger wire to cook her marshmallow.

Metal is a good conductor of heat.

The heat from the fire travelled along the thick metal wire. The wire got so hot that the student had to let go of it.

The young woman in the blue dress is using a wooden rod to hold her marshmallow. Wood does not conduct heat well. The wood in her hand is still cool and the marshmallows are almost done!

Convection:

When heat is moved because something warm is moving, then the heat is being transferred by convection.

Here you see convection happening over a fire. The hot air rises.
This leaves empty space at the bottom of the column of rising air.
Cold air moves into the empty space and the fire warms it.
The newly warmed air also rises.

As the warm air gets close to the ceiling, it loses some heat.
Now this air is cooler. It follows the cool air which is falling.

The cool air falls and then is drawn upwards again.

Convection causes currents of warm and cool air to move.

Notice how convection is happening in this pan. The process is the same in water and in air. It even happens in the hot magma inside the earth.

Remember:

Heat goes higher. Hot air, hot water, and hot rock all tend to rise.

Cold creeps lower. Cold air, cold water, and cool rock all tend to sink.

Radiation:

What happens in space?

Space is so empty that there is not much matter to warm up.

Heat travels by radiation.

Heat waves travel out into the void.
When they strike matter, they make the matter warmer.

The Sun's Radiation:

     The sun emits many kinds of radiation. Heat is only a part of what it emits.

     The sun also emits light, radio waves, gamma radiation, ultraviolet and infrared radiation.

     All these forms of radiation together are called the Solar Wind.


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© 1996,1997, 1998, 1999, 2000, 2002, 2003.   Elizabeth Anne Viau. All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at eviau@earthlink.net .