GENERAL PHYSIOLOGY. 30 



We have, then, two equations. 



(!) TT = R - 



(2) s m = a 



Find s and m. 



(>-* 



(5) --== ^iorar, = m R. 



(6) m = VITJ or, in a similar way, 



Let us take a concrete case, using our 16 cells, each of 

 which has an internal resistance of 4 ohms, how shall we 

 arrange them to get the best results with 16 ohms external 



resistance. 



/ a r /16X4 



m = V-r = -- 



s = = 



We shall therefore arrange the battery in a series of 8 

 pairs, each pair being joined abreast. 



How must they be arranged when there are 64 ohms or 

 more of external resistance? 



How must they be arranged when there are only 4 

 ohms of external resistance? 



What arrangement would you adopt if there is only 1 

 ohm external resistance? 



