CHAPTER XIII 

 EFFECTS OF HEAT. 



28. EXAMPLES OF EXPANSION BY HEAT. 



i. Expansion of solids. (a) Take a metal ball suspended by a chain as 

 shown in Fig. 55, and suspend it by the side of a metal ring, through which 

 it just passes easily. Heat the ball in a laboratory burner for a few minutes 

 and then try to drop it through the ring. It is too large and rests on the 

 ring. Now allow it to cool slowly and notice that after a short time it gets 

 smaller and will slip through. 



Fro. 55. Apparatus for showing FIG. 56. Compound strip of ebonite 

 that a metal ball is larger when hot and wood to show the greater expan- 

 than it is when cold. sion of ebonite when heated. 



(6) Solder a strip of wire or brass, about two feet long, to one of iron of 

 the same length. Straighten the compound strip by hammering ; then heat 

 it. Notice that the strip bends, because the brass expands more than the 

 iron. The same effect can be shown by means of a strip of ebonite glued to 

 a strip of wood, on account of the ebonite expanding more than the wood 

 (Fig. 56). 



(c) Place a heavy mass on one end of the iron bar resting upon one of two 

 blocks, as in Fig. 57. Let the other end bear upon the needle placed upon 



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