1 90 ALTERNATING CURRENTS 



small in comparison with pLi, we may assume that O is practically 

 at the same distance from the centre of the circle as A, so that 

 OP . 00 = AF . AB. 



Now 



FB = -j 77- = pM.^ , 1 ' ^ = 



sm 

 and 



AF = AB - FB =p( L! -^ J = f (Lil* - M 2 ) 



Thus 



and 



AF.AB 



On comparing this with (5), we find 



Considering next equation (4), and putting, approximately, 

 OB = pLi, and utilizing (7), we find 



(9) 



and on comparing this with (6) we get 



K = .Yk_ (10) 



' 



The scales according to which the two currents are to be measured 

 are thus different, the ratio of the corresponding constants being 



Ki = M* 

 K 2 LI 



* Always supposing the secondary winding to contain the same number of turns aa 

 the primary. 



