THE LOCALISATION OF BREAKS AND FAULTS. 



527 



■coil on AB, aud the poiaterd can be moved anywhere on AB, 

 ib follows that we have the same thing as 10 coils each divided 

 into 10 parts, or a total subdivision of the whole into 100 equal 

 parts. Hence the top resistance is marked from to 110. 



Suppose a test battery connected up as shown in Fig. 297 to 

 this set of coils, and that no current passes through the gal- 



;!|i||ii|i|i|i;!|i[t 



Main Battery 



A 110 100 90 



80 70 



60 50 

 F 



876543210 



oTB 



Test Battery 



Hi|ili|iii|i— 



Fig. 297.— Principle of Slides. 



vanometer when the pointers are in the positions shown — 

 namely, the top right-hand pointer F at 60 and the lower 

 pointer P at 8. 



By substituting a standard cell of 1"4 volts in place of the test 

 battery, balance on the galvanometer is obtained with F at and 

 P at 7, and we have 



Standard cell, S divisions=(! volts = 1-4 



Test battery, S^ divisions = e-^volts = l "4 x _^- = 13'6 volts. 



o 7 



