200 Common Science 



objects are pulled toward each other ; so there was an 

 attraction between the comb and the hair, and the 

 hair came over to the comb. As soon as it touched the 

 comb, some of the extra electrons jumped from the comb 

 to the hair. The electrons could not get off the hair 

 easily, so they stayed there. Electrons repel each 

 other drive each other away. So when you had a 

 number of electrons on the end of the comb and a num- 

 ber on the end of the hair, they pushed each other away, 

 and the hair flew from the comb. But when you pinched 

 the hair, the electrons could get off it to your moist 

 hand, which lets electricity through it fairly easily. 

 Then the comb had extra electrons on it and the hair 

 did not ; so the comb pulled the hair over toward it 

 again. 



When you brought the charged comb near your ear, 

 some of the electrons on the comb pushed the others 

 off to your ear, and you heard them snap as they rushed 

 through the air, making it vibrate. 



How lightning and thunder are caused. In thunder- 

 storms the strong currents of rising air blow some of 

 the forming raindrops in the clouds into bits of spray. 

 The tinier droplets get more than their share of electrons 

 when this happens and are carried on up to higher clouds. 

 In this way clouds become charged with electricity. 

 One cloud has on it many more electrons than another 

 cloud that is made, perhaps, of lower, larger droplets. 

 The electricity leaps from the cloud that has the greater 

 number of electrons to the cloud that has the less num- 

 ber, or it leaps from the heavily charged cloud down to 

 a tree or house or the ground. You see the electricity 



