38 



O B = E and A B = E,. The mechan- 

 ical energy given off is proportional to 

 the product A and O D, the latter 

 quantity being the horizontal projection 

 of O B, and obviously equal to R F. 

 Now consider what will happen if 

 some of the load is taken off the ma* 

 chine. The immediate result will 

 evidently be a slight acceleration of the 

 armature, by virtue of which the maximum 

 electromotive force E is induced sooner 

 than previously. In the diagram this 

 effect is represented by the advance of 

 the point B towards B, and a correspond- 

 ing displacement of C towards C,. The 

 length O A will also be slightly altered, 

 viz., decreased until B has come into line 

 with line 0«', and further on increased 

 again. If the whole of the load betake]] 

 off, B will almost coincide with B, and 

 the angle of lag <P will be a maximum ; 

 but the length O A, that is to say, the 

 current, will not be materially differ- 

 ent from its previous value, as can easily 

 be seen from the diagram. Hence it 

 follows that, even when running light, 



