ELECTRIC CIRCUITS 



91 



Similarly the flux produced by unit current in B is 



47T712 



and the inductance of -B is 



X 2 = 



again if all the flux produced by B passes through A, the mutual 

 inductance of B upon A is 



(127) 



and is equal to the mutual inductance of A upon B. 



The leakage flux, that is, the flux which passes out between the 

 two circuits and links with only one of them has been assumed 

 to be very small. In this case 



X 35 = ' : 



^J 2 =91t*. . . (128) 



If the leakage flux is not negligible, the flux fa produced by 

 unit current in A can be divided into two parts <j> Ml and (f> 8l , 



Turns 



o 



2 coii 



O B 

 On, 



QTurns 



FIG. 70. Self and mutual inductance. 



Fig. 70, of which 0^ interlinks with B and < Sl forms a local 

 leakage circuit about A and does not interlink with B' } <f> 8l is 

 the self -inductive flux produced by unit current in A. 



The self-inductance of a circuit is the number of interlinkages 

 with the circuit of the flux produced by unit current in it, which 

 does not interlink with any other circuit; it is the number of 

 interlinkages of the circuit with the stray flux of the leakage flux 

 produced by unit current in itself. 



