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Common Science 



cool, clear days. Rub the 

 comb again, a dozen or 

 more times in quick suc- 

 cession. Now touch it 

 gently to the lobe of your 

 ear. Do you hear the snap 

 as the small spark jumps 

 from the comb to your 

 ear? 



Pull a dry hair out of 

 your head and hold it by 

 one end. Charge your 

 comb by rubbing it again, 

 and bring it near the loose 

 end of the hair. If the 



FIG. 109. When the comb is rubbed on the end of the hair clings to 

 coat, it becomes charged with electricity. the COmb at first, leave it 



clinging until it flies off. Now try to touch the hair with 

 the comb. Next, pinch the end of the hair between your 

 thumb and finger and again bring the charged comb near it. 

 Is the hair attracted or repelled? After touching the comb 

 what does it do ? 



You can get the same effects by rubbing glass or amber on 

 silk. 



Objects negatively and positively charged with elec- 

 tricity. There are probably electrons in everything. 

 But when there is just the usual number of electrons in 

 an object, it acts in an ordinary way and we say that it 

 is not charged with electricity. If there are more than 

 the usual number of electrons on an object, however, we 

 say that it is negatively charged, or that it has a negative 

 charge of electricity on it. But if there are fewer elec- 

 trons than usual in an object, we say that it has a positive 

 charge of electricity on it, or that it is positively charged. 



