Alternate Current Transformer. 41 



of the primary coil=/'i, and SO the thickness of the secondary 

 coil=A2. 



In order to determine L\, L'2, etc., consider first the leakage 

 lines produced by C^ that cross the windows through the spaces 

 occupied by the primary coil. 



If we draw two planes A' A, B'B, Fig. 5, the same distance s 

 on either side of the median plane of the primary, the magnetic 

 forces due to the two portions of the primary coil AP and BO 

 neutralize each other within the space AA'BB', so that the 

 M.M.F. round the circuit AABB' is due to the portion of the 

 primary it encloses and is 



and the flux circulating in this circuit through the elemental 

 rectangle 2p'dz at z is 



as it crosses the window twice. 

 This flux encircles the current 



and as the energy associated with naturally looped flux an(i 

 current is ^ flux x current, the energy of Cj due to the lines 

 through the space occupied by the primary coil is 



•I 



-6 D^<^^-^ ^'-^ 



Thus we see tliat the energy of Cj due to the leakage lines 

 that cross and recross the space occupied by the coil carrying Cj 



is equal to ^ Jh^C^^ x permeance of this space across the window. 



Again the M.M.F. due to Cj, in any circuit that crosses the 

 space occupied by the secondary coil, and completes itself 

 through the iron round the primary coil is uniform, and 

 =47r«iCi and sends through the secondary space (section 2/3'^^) 

 the flux 



