of the Internal Resistance of Cells. 

 But when = 0, V = 0, 



— re — 6E m^i 



175 



= 



v=c 



b + r 

 br 



m 1 + n 1 

 m L ni 



(br 7n L n x \ 



b + r m.+nj' 



If we measure the apparent distance Rj between A and B 

 by any convenient method, and if C be the current sent 

 through this circuit between A and B by the testing arrange- 



y 

 ment, we get Rj equal to ~- ; 



E 1= 



br 



+ 



m^n x 



b + r ' Wi + n, 



Now if we have three circuits (fig. 2) connected together 

 Fig. 2. 



at the point 0, the cell of E.M.F. equal to e and resistance b 

 being the particular one whose resistance is required, and if 

 the resistances m v m 2 , n h n 2 be so adjusted that the points 

 A, B, and C are at the same potential, the apparent resist- 

 ances R 1? R 2 , R 3 between the points A and B, A and C, and 

 B and C, will have the following values : — 



Bi 



R 5 



»,= 



br m-tfi x 



H : — y 



b + r m 1 + n l 



br 



m 2 n 2 



b + r m 2 + n 2 



in Y ny 



+ 



m 2 n 2 



rrii+ny m 2 + nc l i 



