158 Whitehead and Hill — Measurement of Self -Inductance. 







• 



Table V] 

 May 13 



, Coil S. 

 1904. 







R„ 



E" 



r 



R, 



K' 



n 



L 



100-16 



99-42 



1020-2 



1816*9 



1*734-0 



78-121 



1-0345 henrys 



a 



a 



a 



« 



1734-5 



78-303 



1-0359 " 



u 



a 



a 



u 



1760-6 



61-797 



1-0307 " 



a 



cc 



a 



C( 



1734-5 



78-278 



1-0325 " 



a 



a 



a 



1905-3 



1819-3 



81-410 



1-0330 " 



a 



a 



H 



(< 



1818-3 



81-700 



1-0365 " 



a 



It 



(« 



u 



1848-8 



62-604 



1-0354 " 



a 



U 



« 



1616-0 



1529-6 



76-456 



1-0333 " 



a 



(( 



a 



<( 



1528-3 



76-068 



1-0294 " 



a 



a 



u 



a 



1530-1 



76-428 

 Mean 



1-0299 " 

 1-02331 " 



III. 



Method 13.— Method 13 was 



6 



next tried. This is also an 

 absolute method for measur- 

 ing either self -inductance or 

 capacity. It is a zero de- 

 flection method depending 

 on a ninety degree phase 

 difference just as in method 

 14. In fact it differs from 

 that method only in that 

 the fixed coils of the elec- 

 tro dynamometer are no 

 longer in the battery arm of 

 the bridge. The connec- 

 tions are shown in the diagram. Neglecting the self -induct- 

 ance of the fixed and hanging coils of the electrodynamometer, 

 the formula for the method may be deduced as follows. Pro- 

 ceeding as before, we find the ratio of the current in the fixed 

 and hanging coils 



C. 



'jlA^ 



t) _ r (R, 4 R,) + R, (R, + R* + jpL) 

 R'R,-R,ir-«pR,L 



Rationalizing the fraction, and taking the real parts, we have 

 for zero deflection ; 



p a L f = 



R'R,-R,R'} {r(R, + R,) + R,(R,+R') 

 K 2 



We should expect this method not to be as sensitive as Method 

 14, for the reason that we must in general have a smaller current 

 in the fixed coils of the dynamometer. Moreover, since the 

 formula is similar in character to that of Method 14, we would 



