734 



INDUSTRIAL APLLICATIONS. 



If the electromotive force E were of the form E = ^ + IR, this 

 equation will be satisfied for any given value of I, and the current 



x 



will be proportional to -, that is to say, to the number of parts 

 x 



interposed between the poles. 



If the total electromotive force E be represented by a curve 

 (Fig. 264), making the ordinary construction, 



we have 



o c A F 



Fig. 264. 



In order that the value MM' shall be independent of #, the 

 curve ODM must be a right line parallel to CB' that is to say, 

 represented by *? + IR. 



M. Marcel Deprez realises these conditions practically, by closing 

 the inducing coil by two wires, one f traversed by a constant cur- 

 rent /, the other F traversed by the entire current of the machine. 

 If the magnetisation were proportional to the current, we should 

 have 



E = C(/ + I)=C' 



The value of the current / and the coiling of the wire are 

 altered by trial so as to obtain an approximate solution.. A curve 

 is obtained parallel to the preceding, in which that portion DN 

 is utilised which is virtually parallel to CB'. 



