7.
. R (. 7.1).
Rx = ,
Ux Ix , (. . 7.1) , . , Rx (. 7.1 ) , UV IA, :
= ,
UV = Ux + IARA,
IA , , IA = Ix; RA .
Ix,
= + RA = Rx + RA.
∆ Rx = ‒ Rx = RA,
γ = 100.
, , RA << Rx. RA (. 7.1 ) :
= = ; UV = Ux.
,
= = = = .
γ = = ‒ 1 = ‒ ,
γ = 100.
, (. 7.1 ) , RV << Rx. (. 7.1) R 1 .
, , .
. Z, R.
. , , (. 7.2).
:
= ; = = ,
U, I P , .
. , .
(. 7.2): Z x ; W ; R 1 .
12. 2. . . : , , , . , , .
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(. 7.3 ). , ,
I p = .
U Rx. U , . K Rx . 0, I p , R , , .
( 1000 ). 0 K.
(. 7.3 ).
I p = ,
R 1 R p R ; R 2 .
Rx = 0 I p = 0, Rx = ∞
I p max = .
K (Rx = ∞), Rx K. .
. .
. Rx , . (.7.3 ) . Rx ; r 1 r 2 ; R K .
I 1 I 2 :
I 1 = ; I 2 = .
α , ..
α = f ,
α = f = f .
, . . (0,1...0,2)% 20% .
12. 3. . . . 1 . ( 1 ) .
. (. 7.4 ) (. 7.4 ) . :
Rx = R 2 ,
R 2, R 3, R 4 .
R 3/ R 4 () R, , . R 2 , R 3/ R 4. 0,1; 1; 10; 100 1000. .
(. . 7.4 ) R 2 - . K 3, 1 / 100 100 / 1, Rx 0,1 10 6. K 1 , K 2 . , ( ) R 2.
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S M = α/ (∆ Rx / Rx) = (α/ ∆ I )[∆ I / (∆ Rx / Rx)],
α/ ∆ I .
, U , . U () . .
. ( 1 ) , , , . , .
(. 7.4 ). Rx R 0 () ; R 1, R 2, R 3 R 4 , ; R ; r, r 1, r 2, r 3 r 4 ( ); ; I ; I 1 I 2 ; I 3 , .
. r, r 1, r 2, r 3 r 4 , r , , .
, :
I 3 Rx + I 2 R 3 = I 1 R 1;
I 3 R 0 + I 2 R 4 = I 1 R 2;
I 2 (R 3 + R 4) = (I 3 ‒ I 2) r.
Rx,
Rx = R 0 + .
,
d = → 0.
R 1 R 3, R 2 R 4 , , R 1/ R 2 R 3/ R 4 R 1/ R 2. , r , r . d
Rx = R 0 .
r Rx R 0.
, I, , , I. r 1, r 2, r 3 r 4, , R 1 R 2 R 3 R 4 ( 10 ), .
. , , . , , . , , .
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(. 7.5). (. 7.5 a) (Rr 1) , (Rr 2) . Rx, , Rr 1 , Rr 2 Rx.
:
α = f (Ir 1/ Ir 2).
Ir 1 Ir 2 U , α U.
, (. 7.5 ), Rx , , (. 7.5 ). U, α .
, α ∆ Rx, .. Rx
α x = ∆ Rx / Rx.
α . α :
α = c 1 wIr, (7.1)
c 1 , Bs / W; w .
,
S = w k y,
d ; k y , ,
π d 2/ 4 = Sk y/ w.
,
Rr = ρ wl 1/ (π d 2/ 4), (7.2)
ρ ; l 1 .
π d 2/ 4 = ρ wl 1/ Rr. (7.3)
(7.2) (7.3), Sk y/ w = ρ wl 1/ Rr,
w = = c 2 . (7.4)
(7.1) :
α = c 1 c 2 Ir = cIr = c , (7.5)
Pr .
, . , , , ..
R 1 R 2, , R 1 R 2 .
. (. 7.6). R' R" R, . , . Rx ( ) , Rx. . , U r. . , . , , Rx .
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0,5%. , .. , , 0,2% .
.
, , . .
1 ?
2 , ?
3 , ?
4 ?
5 ?