( ) dS ,
dB = BndS = B d S, (11.1)
Bn = Bco s α (α n ), d S =dS n , dS, n . , cosα ( n). , . . , , , , .
S
= . (11.2)
, , n = = nst
B= BS. (11.3)
(): 1 , 1 2, , 1 (1 = 1 2).
: :
. (11.4)
, , ( , , , ).
, () () .
. μ, (120.2),
B = μμnI / l.
S 1= BS,
= 1 n = nBS = μμn 2 IS / l. (11.5)