APPENDIX II. 



The following is a very simple and elegant method of arriving 

 graphically at the results of the integrations in Sections 19, 20, 108 

 and 109. 



Consider a winding ag, Fig. 52, extending over an arc of 180 degs., 

 that is all over the pole-pitch. In each element, extending over an 

 infinitesimally small arc, there is an e. m. f. induced which we shall 



FIG. 52. 



call dc, represented by the infinitesimally small vector AB perpen- 

 dicular to the element of the winding ab. We can see at a glance 



that the vector-sum, or the expression ( de, is equal to AG, and that 

 the algebraic sum of the e. m. f.'s induced in the elements is equal 



to the arc ABC D G, since in the latter case the elements have to 



96 



