24-2 On Copper-zinc and Platina-zinc Voltaic Pairs. 



let tt be the actual current, k the current measured by the 

 balance, we have the equation 



from which is deduced L l = — (1— */ Y—Mcy). For my 



ly 



balance I have found, by a series of observations, y 

 = 0-00004228 {Bulletin Sc. de V Acad. Sc. torn. v. p. 375.). 



The following table contains the experiments made with 

 the voltaic combinations in question. The first column con- 

 tains the resistances, L, of the helices which serve as conjunc- 

 tive wire, and which had been found by other experiments ; 

 the two other columns contain the forces of the effective 

 currents, or of the currents measured in grammes, and cor- 

 rected according to the formula above indicated. 



L. 



Force of 



the pair, 



Copper-zinc. 



Force of 



the pair, 



Platina-zinc. 



23-1 

 135*3 



gr. 



0-380 

 0-097 



gr. 



0*395 

 0-135 



Let A, A' be the electro- motive forces, X, X' the resistances 



of the pair itself, we shall have, according to Ohm's formula, 



the four following equations : 



A A' 



= 380 rr-^r = 395 



X+23'l 

 A 



= 97 



A/+23-1 



A' 



135, 



X+135-3 X'+135*3 



whence A = 14610, X = 15*35, A' = 23000, X' = 35 ; or 



taking X as the unit of surface, which is here 36 square inches, 

 Let s be the total surface of a pile, 



35^ 

 36 

 z the number of pairs, C the force of the current, L any re- 



Z A 5 



sistance, we have C = ■ 2 ^, j — • From this equation we 



find, that the maximum of force is obtained, if the pile be 



arranged so that = L, i. e. that the total resistance of the 



pile shall be equal to the resistance of the conductor, what- 

 ever its nature may be, this resistance being one which is in- 

 terposed in the circuit, and not belonging to the pile. As for 



