546 MEASUREMENT OF RESISTANCES IN ABSOLUTE VALUE. 



Formula (10) gives thus 



R H _wGS 



G tan 8 ' 



The method is very simple. It is not, however, quite true that 

 the maximum electromotive force corresponds exactly to the passage 

 of the frame through the meridian. Let us assume that the ends 

 of the wire, instead of being free, communicate separately with a 

 condenser C. The problem is thus solved by the equations of 993, 

 in which R' = oo . The electromotive force of induction being 



E = wHS sin 27r = wHS sin o>/, 

 T 



and V the difference of potential of the armatures, the current I 

 which traverses the circuit, is equal to C . The equation of 

 induction becomes in that case 



We may write 



and following the usual course, we find 



CRo> 



CL - + CR + V = E. 

 dt* dt 



tan 



A 2 



C 2 R 2 



There is consequently a difference of phase, or a retardation, 

 which strictly only vanishes provided the capacity is zero. This 

 retardation, as well as the maximum value of V, are functions of the 

 capacity, or of the coefficient of self-induction. The moment the 

 frame passes through the meridian, the difference of potential of 



