284 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



ratio of secondary to primary turns of helix as ordinates, and secondary 

 resistance as abscissae. The ordinate scale is, as has been pointed out, 

 practically proportional to the mutual inductance between the two 

 circuits, but, for the sake of definite units, is expressed in terms of 

 turns of helix. The curves were derived by taking the intersections of 

 the horizontal, 1, 1.5, 2, 3, 4, and 5 ampere coordinate lines with the 



FiGUEE 10. Power Curves Derived from Figure 8. 



A 2 = 100 meters. 

 lo = .55 ampere. 

 Ci = 175 X 10-5 fi.f. 

 C2 = 86 X 10-5 M./. 



secondary current curves of Figure 8, and plotting to the correspond- 

 ing secondary resistances. The dot-and-dash curve is drawn through 

 the points of maximum slope of the constant current curves, and is the 

 locus of the points representing maximum power output. It is ap- 

 proximately a parabola, expressible in the form 



( 



j^ 1 <x- It 2, or, since i\ j = 4 = const., 

 iVa^ = -ff'i 7?2 where Ki is a constant. 



This is the same expression which was previously derived by assuming 

 the existence of a maximum permissible reaction of the secondary cur- 



