4-B] 



CIRCLE DIAGRAM. 



125 



a series circuit, being the same as Fig. 9, Exp. 4-A, and Fig. 3, 

 Exp. 3~B, for the alternator; compare, also, Fig. 9, Exp. 5~B 

 and the transformer diagrams, Exp. 5~C. As explained in n, 

 OCA is not an exact right angle. 



10. For a second set of readings, locate the points B', C', D', 

 in the same way as the points B, C, D were located. 



Locate points in this manner for all the readings, thus defining 

 the curves in Fig. 2, which are the loci of the points B, C and D. 



Method of plotting 

 results. 



FIG. 2. Circle diagram for a constant po- 

 tential circuit with constant reactance, when 

 resistance is varied. 



11. It is seen that, as the resistance is decreased, the cur- 

 rent increases and lags more and more behind the electromotive 

 force. If the impressed electromotive force, and hence the current 

 which flows, are sinusoidal, and if there is no power lost in the 

 reactance coil R 2 L 2 , except R 2 I 2 (supplied by the power electro- 

 motive force BC = R 2 I), OCA will be a right triangle. In this 

 case, the locus of C will be a semicircle with diameter OA=E, 



