Measurements of Inductance. 



531 



§ 12. Brillouin's device for meeting the difficulty in § 11 

 that M has to be less than L is to put the second coil in the 



"-A/VWWW 



same branch as T, but this makes a continuous balance 

 impossible. The equations at short-circuiting are : — 



(Q + S)y + S*=0, B,x-$y-gl -(G+B+S>=0, 



Initially i=/, £ = 0, s=0, u= 5±?/, and ~ = — ; , so that 

 the c's cannot vanish. ■"• 9 



§ 13. By a method due to Niven the M o£ two coils is 

 sometimes compared with the inductance of a third, L, 



x+y 



placed in a balanced quadrilateral. Taking N for the in- 

 ductance of that one of the pair which is joined in parallel 

 with the galvanometer, and n for the inductance of the one 

 in the battery arm, and the other symbols being as shown, 



2 2 



