U){) Whitehead and Hill — Measurement of Self- Inductance. 



Method L— See fig. 7. 



L _ [r(R, + R') + R,(r + R,)] [R'(R, + R ,)+R* (R, + R')] 

 C~~ (R^R' + RJ* 



The trouble with this method was its lack of sensibility. Vari- 

 ous values of resistances and coils were tried, but with the 



arrangement, which was as 

 sensitive as possible, the re- 

 sistances could not be ad- 

 justed closer than 1/5 per 

 cent. This also when the 

 maximum current was 

 flowing through the net- 

 work. It will be noted 

 that the formula is quite 

 similar to that of Method 

 14, so we should expect 



the value of -^ to be affected in the same way as was L by a 



slight change in one or more of the resistances. The values 

 of the resistances which seemed to give the most sensitive 

 arrangement when coil F was compared with a ^-microfarad 

 mica condenser were, 



R' = 336 ohms 

 R = 1200 ohms 



W^ 



R ff = 100 ohms rr R 

 r =3900 ohms 



Method 2.— See fig. 8. 

 When L = '570 and 

 C = ^-microfarad. The 

 values of the resistances 

 which seemed to give the 

 most sensitive arrange- 

 ment were, 



R" = R /y = 100 ohms 



R =± 1600 ohms 



R' = about 1600 ohms 



This method did not seem to be capable of adjustment much 

 closer than 1 per cent even when the current through the net- 

 work was *08 amp., which was much too large to avoid heating. 



Method 3.— See fig. 9. 



C" 



This is the simplest of the methods for determining 

 formula is 



~ =rR\ 



The 



As has already been stated, this method has been used with 



