DETAILED STUDY OF OPERATION WITH NORMAL LOAD 45 



By substitution, we have 



P 2 R 



2 -' 



COS f COS J f 



or 



2 COS f/ COS" f 



from which it can be seen that the curve is a circle whose center has 

 the following co-ordinates: 



Ei 



x = 



2 cos 



Each circle has for its center the point of intersection, N, of the 

 right lines ON and OAi, both making the angle f with OA\; and the 

 radius of this circle is 



(19) 



This result is also easily obtained by geometry. 



As for the lines of constant electric-power, P\ (applied at the 

 terminals), they are evidently straight lines perpendicular to A\N (none 

 of which has been drawn on the diagram except the line PI=O); 

 because they are defined by the simple condition that the current 

 which is active with respect to E\, .(i.e., i), is constant. 



The expression (19) can be calculated algebraically, for various 

 values of P^, or it can even be determined graphically by means of 

 rectangular triangles. It is convenient to express the power P% as a 

 function of the maximum power which can be obtained by making 

 2 vary, E\ being supposed to remain constant. As will be seen later 

 this power, which will be designated by the letter P, has the following 

 value: 



It is easy to construct a series of equipotential lines corresponding to 

 the given values of P^ and thus to predetermine the variations of 

 power resulting from the displacements of the point A%. 

 The radius p can then be written, 



