32 



B represents to the same scale the loss 

 of electromotive force in the armature 

 when the machine is giving its full cur- 

 rent^ and O T> the corresponding electro- 

 motive force of self-induction. Make B 

 C parallel with and equal to O D, and 

 describe circles over the diameters O A, 

 O B, O D, and O C ; then a straight line 



Fig. 8 



revolving round O as a center, in the 

 direction of the arrow, is cut by these 

 various circles in such a way that the 

 segments represent the respective values 

 of the different electromotive forces at 

 any moment. Thus, at the time when 

 the angular position a has been readied, 

 the induced electromotive force is Oc, the 

 effective electromotive force is Ob and 



