ELECTRICAL INVENTIONS 



233 



WHEN DISCHARGING 



PbA 



decomposes 

 yielding 



H 2 So 4 Pb 2 s <- Anode 



decomposes 



Cathode unites with \|/ ^ 



->Pb <- SO 4 H 2 



forming PbSo 4 unite to form 



H 2 O 



The lead plates in stationary storage batteries are usually 

 honeycombed in order that they may carry a larger amount of 

 peroxide and may also 

 present a greater surface 

 for chemical action. But 

 in storage batteries that 

 are subject to constant 

 jar, like those of automo- 

 biles, plain plates must be 

 used since the jarring 

 detaches flakes of the 

 peroxide which are likely 

 to lodge between the 

 anode and cathode and so 

 short-circuit the battery. 

 Batteries in automobiles 

 must, therefore, be fre- 

 quently recharged, while 

 stationary batteries can 



. , , .-, . n FIG. go. Diagram of an electric motor 



take a charge that will reduced ^ sim p le terms, 

 last a long time. 



When Ampere discovered that a current flowing in a wire 

 makes the wire behave as a magnet, the foundation was laid for 

 the electric motor. An electric motor reduced to very simple 

 terms may be thus made (Fig. 99). Lay two bar magnets on 

 the edge of a table with the north pole of one and the south pole 

 of the other projecting over the edge an inch or so, and the two 

 poles about 2 inches apart. Take a piece of i6-gauge insulated 



