726 



INDUSTRIAL APPLICATIONS. 



<(I + / ); it is the same curve (Fig. 257) the origin of which has 

 been displaced by OC = / . We have again 



r 

 by making the same construction, starting from the point C, we 



shall get the value MP of E I} and the corresponding intensity CP. 

 In this case the problem is always possible. 



If the useful work is an electromotive force to be overcome e, 

 the equation of the current 



I 



R 



gives then 



R F ' 

 =El ~ 



Starting from a point C', at a distance CC ; = - from the origin, we 

 draw the right line C'B' (Fig. 258) in a direction a, given by the 



n 



condition tan a = ; we have 



1 -- = MP'. 

 n 



and 



CP. 



