METHODS OF HEATING BODIES 



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move about from one place to another is called heating by 

 convection currents. When you fill a teakettle with cold 

 water, and set it on the stove, will there be any movement 

 of the water while it is heating ? Where will the warmest 

 water always be found, at the top or bottom ? Where will 

 the convection current stop ? When it all reaches the same 

 temperature. When will the convection current of air in a 

 room stop ? When you light a lamp, what is the direc- 

 tion of the convection current which carries fresh air to the 

 flame? Determine this by holding a smoking match or 

 piece of punk below the burner and above the chimney. 



There is still another method of heating bodies. Hold 

 the end of the poker in the stove till it is quite hot. Take 

 it out and hold your hand above it. Can you feel any heat 

 coming from it ? Hold your hand below and at the sides. 

 Is heat coming from it in all directions? This kind of 

 heat is called radiant heat. It is the heat that streams off 

 in straight lines from any heated body. It does not have 

 to have air to travel then. It is the kind of heat that we 

 get from the sun. 



Does a stove radiate any heat? You have only, to 

 stand in front of a hot stove to feel the heat striking your 

 face. Set a chair about two feet from a hot stove. After 

 half an hour or more feel the chair. How has it been 

 heated? Chiefly by radiation from the stove. How is 

 the schoolroom heated when it has a stove in it ? A little 

 discussion will show that it is heated by convection currents 

 and radiation. 



When the rays of heat strike a body, what becomes of 

 them ? What did the chair do with the rays from the hot 

 stove? It absorbed them, or at least part of them. No 



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