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16. R I. . . x<<R x>>R.

 
 

 

 


.

- dl, ( ) dB=(m0/4p)(Idl/r2)sina. , . sina=R/r .

B(x)=(m0/2)IR2/r3=(m0/2)IR2/(R2+x2)3/2

x<<R B(x)=m0I/2R, x>>R B(x)=(m0/2)IR2/x3.

 

17. I = 3 . , L = 10 .

, D I. R , , r dl, da=dl/r , dl . a - , , R=rcosa. - dl

dB=(m0/4p)(Idl/r2)= (m0/4p)(Icosa da/R).

B=(m0/4p)(I/R)(sina1 - sina2).

a1 a2 - , .

, L , , . .

a1=p/2, a2=-p/4, R=Lcos(p/4),

= 2 10-6(3/0.1)0.42=2.48 10-5

 

 

18. R j. r .

. . . :

 

I=pR2j .

r<R

r>R

 

 

19. R . I, . r .

. . . :

0<r<R

0<r<R

, B(r)=0 r>R,

 


20. N , I. R1, - R2. r .

R = (R2 - R1)/2 , . , , , .. , . . . . r 2prB(r) , , , NI, , , . , , . R1 <r< R2 . n=NI/2pr , . i=nI .

 

 

21. R L, . n. , I. : R=1 , L=50 , n=15 /, I=1 .

, R , n . B= m0nI, B =0.

p=B2/2m0. , , S=2pRL

F=pS=m0(nI)2S/2=pm0(nI)2RL

:

B=1.256 10-6 15 1=1.88 10-5 p=1.41 10-4/2 F=4.44 10-6

 

 





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