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Conduction of heat in metal vs. a black paper cover

 
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mcouris



Joined: 16 Aug 2009
Posts: 4
Location: Palatine, IL

PostPosted: Wed Aug 26, 2009 12:55 pm    Post subject: Conduction of heat in metal vs. a black paper cover Reply with quote

Two test tubes are placed in bright sunlight for fifteen minutes. One is completely covered in aluminum foil, and the other is completely covered in black paper. I am told that the temperature rises most rapidly in the test tube covered in black paper. Why is this? I know that black color absorbs more heat than light colors, but why would the black paper absorb more heat than a great conductor of heat such as metal foil?
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hepcj
Site Admin


Joined: 23 Jun 2007
Posts: 125

PostPosted: Thu Aug 27, 2009 10:19 am    Post subject: Reply with quote

There are three ways in which heat can be transferred to an object. These are:
conduction - heat transfer by virtue of kinetic energy being passed along the object by microscopic collisions of the particles which make up the object.
convection - heat transfer by heat being taken to the object. Most commonly heat rising through the air to heat another object.
radiation - heat energy is transferred to another object by infra-red radiation.
Black paper absorbed the energy through radiation.
Metal although a good conductor of heat is also a reflector. As the main mechanism for heat transfer is through radiation, in this case, the black paper will be the most effective method of heating.
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