110 



KENNELLY AND VELANDER— POTENTIOMETER 



been already pointed out. The impedance of the combination will 

 vary over the circle LUSM, Fig. gb, from OL with c = o to OM = o 

 with c=cc. The diametral maximum impedance OR or 2147 



Zlf^tct,^ 



Fig. ga. Vector admit- 

 tance of / and c in par- 

 allel as c is varied from 

 zero to infinity. 



Fig. gb. Vector impedance of / and c in par- 

 allel as c is varied from zero to infinity. Vector 

 inversion of Fig. ga. 



ohms, occurs at the value of c (1.317^1/) at which On, Fig. ga, is 

 horizontal, and at which value the vector admittance in ga has mini- 

 mum size. At this value of c, the admittance of the Ic combination 

 is a minimum, its impedance a maximum, and the p.d. at terminals 

 qq' in phase with the main current. This condition occurs when 

 the susceptance of the condenser jcw is equal and opposite to the 

 susceptance of the coil. Thus 



•-77, 



y= 



;'.<jo 



lo 



-J 



r+jlui r''+l-oi- r--\-l-or ' r-^-l-d" 



= g—jb mhos Z (8) 



