CHAPTER IV 



TRANSFER OF HEAT 



Heat may be transferred from one substance to 

 another in three different ways: conduction, convec- 

 tion, and radiation. We shall consider only the first 

 two of these ways. 



Conduction. If one end of an iron rod is held in 

 the hand and the other end is placed in a flame, the 

 end held in the hand soon becomes hot. Evidently the 

 heat from the fire travels along the rod from the flame 

 to the hand. 



When heat travels from one body to another, with 

 which it is in contact, or from one part of a body to 

 another, the process is called conduction. Heat flows 

 from a warmer to a cooler part. Coldness is merely 

 absence of heat. 



A body which allows the heat to travel through it 

 is called a conductor. There is a great difference in 

 conductors, some being very good, others so poor as to 

 seem to allow no heat to pass through them. Most 

 metals are very good conductors of heat. Different 

 metals, however, vary greatly in the rapidity with which 

 they conduct heat. Copper conducts heat about four 



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