THE LOCALISATION OF BREAKS AND FAULTS. 407 



total resistance of the break, namely, the resistance of the 

 exposed conductor and the resistance due to the testing 

 current acting against the polarisation potential, considered 

 together as one quantity, which he found varied inversely as 

 the l"3th root of the testing current for constant areas of 

 exposure. In the diagram. Fig. 239, the horizontal lines 

 represent the resistances taken into account in Schaefer's 

 test. The first line indicates the test with the lower current 

 (c) and the second line that with the larger current (wc). The 

 resistance of the exposure (/) with the resistance due to 



polarisation ( - 1 are bracketed together to indicate the total 



resistance (F) of the break dealt with in this test. With 

 testing current equal to wc the total resistance of the break by 



Schaefer's law falls to j-— , and this is due partly to the fall 

 in the exposure resistance determined by Kennelly and 



£ 





Fig. 239. — Analj^sis of Schaefer's Break Test. 



partly to the fall in the polarisation resistance consequent 

 upon increase of testing current, taking into account the rise 

 in potential due to increase of current above referred to. This 

 manner of showing the resistances in line is intended to fix 

 ideas as to the several parts of the whole included in the 

 bridge balance and their approximate variation with current. 

 It must not be taken too literally to mean that the several 

 resistances are all in series. From the application of the law 



to the apparent resistance — , when the current is nc this re- 



\j 

 sistance becomes 



E 'Vn E 1 



G n G Vw 

 and as the whole resistance (F) varies as a similar function of 

 n, it follows that if the exposure and polarisation resistances 

 were in series, either the exposure resistance would vary in- 



