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: , .
: , 906, -2, ().
, , . , . , .
. , , 䳺 σ0, :
E=F/σ0,
, . σ, r :
E=σ/4πεε0(r^2).
. , , , , :
φ=A/σ0,
σ0 , .
φ r , , σ, :
R.
, , . . , , 䳺 , .
, . .
, , ( ). , , . , , . , , , .
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, . . ?
. , , , . , , .
, j :
div j = 0.
, (σ=const), :
div j = div (σ E) = σdiv j = 0,
div j = 0. (5.1)
rot E = 0. (5.2)
, (5.1) (5.2). .
г (5.1) (5.2), , , . . , , . , , , ᒺ , . .
, , . , , .
, . , ( ), , , . . , , , .
, . , . , , . , , . (), .
, , . , 䒺 . . ˳ . , .
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, . r . r j (r)
j (r) = I/2πrd,
, ; d .
r
E (r) = j (r)/σ, E (r) = I/2πrdσ,
σ .
, , , , . , :
E = -grad φ,
:
E (r) = -dφ (r)/dr = -dU (r)/dr,
U (r) = -∫ E (r)dr = (I/2 πσd) * (ln r/r),
r .
U (r) E (r) , , σ, , d r, r, U0, (r , U0 - ):
U0 = U (r) = (I/2 πσd) * ln (r/r); (5.3)
U (r) = (U0/(ln r/)) * (ln r/r); (5.4)
E (r) = (U0/(ln r/r)) * (1/r). (5.5)
U = U (r) E = E (r) , (5.4) (5.5).