116 



KENNELLY AND VELAXDER— POTENTIOMETER 



The connections for the test are indicated in Fig. ii. The high- 

 resistance box AB of 100,000 ohms, is divided into 10 coils of 10,000 

 ohms each. The end B is grounded, and also connected to the re- 

 sistance tap of the potentiometer. The exploring tap, passing 



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TruJUA^a^ 



600 



700 



^00 



Fig. 10. Vector voltage drop observed along a sectioned high resistance 

 box of 100,000 ohms in 10 coils of 10,000 ohms each, at the frequency of 2,010 

 cycles per second. Crosses indicate observed, and circles computed values. 



through the vibration galvanometer, makes contact in succession 

 with the junctions i, 2, 3 . . . 10 of the resistance coils, Fig. 11. 



The results of an exploration, at 2010-^, are presented in Fig. 

 10. With the potential of the grounded point B at the origin, the 

 potential at A was 855 + ;98 millivolts. If the fall of potential 

 along the coils were regular, the intermediate potentials should have 

 fallen on the straight line AB, whereas they actually fell upon the 

 curve 5, I, 2, 3 ... ^. The vector deviations are indicated at 

 each junction, and they afifect both size and slope. The reason for 

 this behavior evidently is that, as indicated in Fig. loa, the resist- 

 ance box resembles an artificial line, in which the line sections are 

 resistances shunted by condensers ; while each section has a con- 

 denser leak to ground. The observations indicate that each 10,000- 

 ohm section subtends, at this frequency, an average hyperbolic angle 

 of 0.13/15°, which would be accounted for by a shunting con- 

 denser of 13.7 millimicrofarads per section, and a leak condenser of 

 0.268 millimicrofarad. The results indicate that the drop of poten- 

 tial in the section nearest to the ground point is very distinctly less 

 than one tenth of the total drop BA, and that in the sections near A 



