108 



KENNELLY AND VELANDER— POTENTIOMETER 



The circular graph of Fig. yh is a current locus to OR as stand- 

 ard current phase. The same graph may, however, be regarded as 



Fig. jc. Vector circular loci of main and branch currents in the circuit of 

 Fig. 7a, as the condenser c is varied. 



an admittance locus to Ok as standard admittance phase, if we 

 change the scale of coordinates accordingly, since 



Y = 



ohms Z (7) 



and E is the e.m.f. in the circuit, 3. 744 Z I9°.4 volts, which was kept 

 constant both in size and in slope during the observations. If, re- 

 garding Fig. yb as an admittance graph to the proper scale, we take 

 the reciprocals of successive vector values, we obtain therefrom an 

 impedance graph which must also be circular, according to the theory 

 of geometrical inversion. Fig. 8 shows the vector impedance graph 

 so obtained. It represents the vector impedance in the main circuit 

 of Fig. ya when the condenser c is varied. At c^ 00, the vector 



