120 



KEXNELLY AND VELANDER— POTENTIOMETER 



been covered, if a condenser had been substituted for the inductance 

 load. 



Fig 13 shows why a circular current graph might be expected in 

 this case at the receiving end. The denominator in formula (17) 

 contains the vector sum of a fixed impedence ^r^ sinh 6 and the vari- 

 able impedance jLio cosh 8. In this term oj and cosh 6 are constant, 

 so that L is the only variable. The vector OA, Fig. 13, represents 

 s^, sinh 0. AC is the vector jLoi cosh 0, for L corresponding to Lw/R 

 = 0.4. The vector sum s^ sinh 9 -\- jLm cosh B is then OC. To suc- 

 cessive values of L, from L = o to L = 0.175 henry, correspond suc- 

 cessive distances from A, along the straight line AB. The vector 

 locus of the sum appearing in the denominator of (17), is therefore 

 a straight line. The reciprocal of this vector sum must conse- 

 quently follow a circular locus, and corresponds to the circular locus 

 of Fig. 12. OP is the perpendicular from the origin to the line AB. 

 The point P thus marks a minimum receiving-end impedance, and 

 a maximum received current. This corresponds to a certain type 

 of resonance. 



^u.C.1. 



J.o //i 



Fig. 14. Resonance curve of received current strength squared against the 

 ratio of receiving end reactance to total resistance. 



