ELECTRIC BATTERY 



1982 



ELECTRIC BATTERY 



GRAVITY CELL 



solution of sulphuric acid. Hydrogen is set 

 free by the action of the acid on the zinc, as in 

 the simple vol- 

 taic cell, but 

 when the hydro- 

 gen ions reach 

 the copper sul- 

 phate they ex- 

 change places 

 with copper ions 

 (see ION). These 

 copper ions go to 

 the copper plate, 

 carrying positive 

 charges. Copper 

 is thus added to 

 the copper plate, 

 making it heavier 

 but in no way in- 

 terfering with the 

 current. The 

 copper and cop- 

 per sulphate are placed in the bottom of a 

 glass jar, the zinc and sulphuric acid above 

 the copper sulphate. 



Gravity aids in keeping the liquids separate, 

 the copper sulphate solution being heavier than 

 the sulphuric acid solution. A gravity cell can 

 be set up simply by placing the copper plate in 

 the bottom of the jar and the zinc plate near 

 the top, placing some crystals of copper sul- 

 phate in the jar and filling it with water. It 

 is a number of 

 hours after the 

 cell thus set up 

 is placed on a 

 closed circuit be- 

 fore it is ready to 

 give a strong cur- 

 rent, but it will 

 then furnish cur- 

 rent for a num- 

 ber of weeks. 

 The only atten- 

 tion necessary is 

 to keep the jar 

 filled with water 

 and add copper 

 sulphate crystals 

 from time to 

 time, if the blue 



-a 



DANIELL CELL. 



color disappears. A small quantity of sulphuric 

 acid is formed by the action of the copper 

 sulphate, which works its way up to the zinc. 

 The action of the cell is then the same as that 

 described above. 



Other Cells. The so-called Danicll cell is 

 made of the same materials as the gravity cell, 

 the liquids being 

 separated by a por- 

 ous cup. Gravity 

 cells are used in 

 short-distance teleg- 

 raphy and in block 

 signaling. 



In the Edison- 

 Lalande cell the 

 negative plate is 

 made of copper 

 oxide. The hydro- 

 gen which comes to /.;.'.; ^;CV t-J+C? 

 this plate when the 

 cell is working is 

 disposed of by com- 

 bining with the oxy- 

 gen of the copper 

 oxide so that the 

 cell does not polar- 

 ize. This cell will 

 work on either open- 

 or closed-circuit. 



Black manganese 



DRY BATTERY 

 (a) Carbon. 



_,. (6) Porous substance 



Ine Bunsen bat- with sal ammoniac. 



tery is a form of fg | inc ' 

 closed -circuit bat- dioxide, 

 tery formerly used but now replaced by the 

 cells mentioned above. The Grove cell, which 

 preceded the Bunsen cell, consisted of a zinc 

 plate in sulphuric acid and a platinum plate in 

 nitric acid, one of 

 the liquids being 

 in a porous cup. 

 Bunsen and 

 Cooper, working 

 independ- 

 ently, improved 

 this cell for prac- 

 tical purposes by 

 using carbon in 

 place of plat- 

 inum. The nitric 

 acid prevents 

 polarization, hy- 

 drogen combining LE CLANCHfi BATTERY 

 with some of the oxygen of the acid and form- 

 ing water instead of collecting on the carbon 

 plate. 



Of open-circuit cells the dry cell and the 

 Le Clanche cell are the most important. The 

 outside of a dry cell is a zinc cup which forms 

 the zinc plate of the cell and at the same time 

 contains the other elements of the cell. Within 

 the zinc cup is, first, a porous substance con- 



