MEASUREMENTS AT TELEPHONIC FREQUENCIES. 101 



pedance in the working circuit of Fig. 2 is 



Z=R + j 



(-^) 



ohms Z (5) 



If we keep r, L and w constant, but vary C, the impedance will ad- 

 vance vectorially along a straight line parallel to the / axis, or react- 

 ance axis. This is shown in Fig. 3, where distances along the hori- 

 zontal real axis represent values of resistance R; while distances 

 along the ; axis represent values of reactance. As the value of C 



Fig. 3. Planevector impedance locus of a simple RLC circuit in which the 

 capacitance is varied. 



was changed from infinity to 0.03 X lO"*' farad, the vector value of 

 impedance moves along the straight line abd e. The impedance Z 



