MAGNETISM AND ELECTRICITY 



177 



COVlRWtlOlO 

 STUff IN6 BOX 



When the battery is fully charged and in good condition, 

 the positive plate is a dark reddish brown or chocolate color, 

 while the negative plate is slate-colored. On discharging 

 the battery, the SO 3 

 is obtained from sul- 

 phuric acid, which 

 combines with 

 water and forms 

 lead sulphate with 

 lead. When the 

 battery is recharged 

 the current releases 

 the SO 3 , restoring 

 the plates to their 

 previous condition. 

 Storage batteries 

 are measured in 

 ampere-hours . 

 Thus a 100 ampere- 

 hour battery will 

 give a continuous 

 discharge of 12J^ 

 amperes for 8 hrs. 

 Theoretically, it should give a discharge of 25 amperes for 

 4 hrs., or of 50 amperes for 2 hrs. 



The capacity of a cell is proportional to the exposed area 

 of the plates, the number of plates, and the active material 

 present. 



211. Arrangement of Electrical Apparatus. A group of 

 cells or electrical apparatus may be arranged in different 

 ways. The wire from the zinc of the first cell may be 



ass 



FIG. 76. One Form of Storage Battery. 



