J 252 



stance". The real resistance is therefore repiesented by the angle 

 which the straight part of the characteristic forms with the axis of 



Fig. 2. 



ordinates while the point of intersection of the extension of this 

 straight part with the axis of abscissae indicates the maxiinnm E.M.F. 

 of polarisation. If the cnrrent is sent throngh this electioljtic detector 

 in the other direction, the same cnrve will be obtained ^), which 

 for this detector is symmetrical with i-espect to the origin. When 

 using a constant auxiliary E.M.F., the centie can he brought 

 outside the origin. The same voltage will then yield a different 

 intensity of current according to the direction in which it is applied, 

 i.e. the electrolytic detector ivith mixlJidry E.M.F. has a unidirec- 

 tional resistance. 



If the platinunipoint is replaced by a thin wire of copper or 

 molybdenum the detector will also exhibit an unsymmetrical charac- 

 teristic without any auxiliary E.M.F. It will then have the shape 

 of the curve Fl (cf. fig. 3 on the folding plate). The real resistance "'') 

 is equal in both directions as will appear from the fact that the 

 two linear parts are parallel, but the maximum value of the E.M.F. 

 of polarisation is different in the two cases and amounts to about 



^) The platinum point should not be taken too small here. 



2) Remark. As the readings of the voltameter and milliammeter are plotted 

 directly, the "real resistances" R derived from the characteristics of fig. 3 are all 

 of them 100 Ohms too large, as obviously the resistance of the milliammeter 

 (100 il) is included. This does not however influence the above discussion. 



