196 



GENERAL SCIENCE 



FIG. 164. 



particles of electricity) of the shells are attracted by the 

 positively charged rod, thus producing an excess of elec- 

 trons on A and a lack of electrons on B. If the rod is 

 taken away, the electrons which have been drawn to A 



will flow back to their 

 places and neither shell 

 will show any charge. 

 If, however, the shells 

 are separated while the 

 rod is near the shell A, 

 each shell will be per- 

 manently electrified, A 

 having a negative 

 charge and B a posi- 

 tive charge. The charges on the shells may be tested in 

 the usual way. 



A similar experiment may be performed with one foil- 

 covered shell. When the positively charged rod 

 brought near one end of 

 the shell (Figure 165), the 

 electrons are drawn to 

 that end, producing a lack 

 of electrons at the other 

 end. Now while the rod is 

 still in this position, touch 

 the opposite end with the 

 finger. Electrons will flow 

 from the finger to the 

 shell to make up the defi- 

 ciency of electrons on that end. When the rod is taken 

 away, the shell will be found to be negatively electrified. 

 Charging a body in this way is called charging by 

 induction. 



is 



FIG. 165. Electrons are drawn toward 

 the positively charged glass rod. 



