MEASUREMENT OF POLARIZATION. 425 



In order to eliminate the resistance r, it is sufficient to replace p 

 by another value />', and to determine the corresponding value m'. 

 We have then 



e r + p r + p p-p 



~ m Q t 

 m m 



( p -- p -\ 



\rn m' j 



We-rjciight, moreover, determine the ratio of the differences of 

 potential A and <? by an electrometer or by a galvanometer of high 

 resistance. 



1020. INVESTIGATION OF A BATTERY AT WORK. When a 

 battery is at work it might be useful to investigate its properties, 

 taking as much care as possible not to open it. 



Let us consider the case of an effective electromotive force E 

 and resistance R closed by a circuit of resistance p, and let I be 

 the strength of the current. The difference of potential at the two 

 terminals is 



If the current is opened, the difference of potential V between the 

 same points, before the polarization has time to disappear, is 



The values of V and V being determined by comparison with 

 a standard, by means of an electrometer or a galvanometer of high 

 resistance, we have 



If the battery consists of n couples arranged in series, the 

 electromotive forces of which are e lt e 2 ..., e n and the resistances 

 /i, ^ 2 r n-> tne preceding experiment will give first 



