' Q j1 , j2, :
'= .
A = Q (j1 j2). '
A' = Q (j1 j2)= Q (j2 j1). (1)
; .
j1 j2 (1) , Q = Q2,
. (2)
, 1/(4pe 0)=9×109 /, (2)
A '=180 .
12. Q =10 1 2 (. 34), s =0,4 / 2 , l 3 .
. .
1- . Q 1 j1 2 j2
A = Q (j1 j2). (1)
1 2 I II. , .
j1 j2 = El,(2)
; l .
E =s/e 0. (2) j1 j2 (1),
A=Q (s/e0) l.
2- . , , Q, . 1 2
A = FDr cosa, (3)
F , ; D r Q 1 2; a . F=QE=Q(s / e0). F (3), , D r cosa= l,
A=Q (s/e0) l. (4)
, .
(4) Q, s, e 0 l,
A =13,6 .
13. , R, t =10 /. j , , . l 1/3 15 .
. , , (. 35). dl. dQ=tdl, , .
|
|
. , dQ:
,
-, dl , . :
,
().
:
.
l. .
, (1)
. r = R =const dl=RdJ.
.
(1) , , 0 p/3, ;
.
R (3 l= 2p R),
.
, t l ,
E =2,18 /.
. dj, dQ :
r R :
.
l= 2 pR/ 3,
j =t /(6e 0).
,
j =188 .
14. R= 1, t=20 /. , a1 =0,5 2 =2 , .
. . , ,
, dj = dr.
, , r1 r2 ;
. (1)
,
.
(1),
(2)
r2 r1 , , :
r1=R+a1= 1,5 ; r2 = R + a2 =3.
t, e 0, r1 r2 (2) ,
j1 j2 =250 .
15. , t =0,1 /. j , , .
. , , ,
, (1)
, . dl, tdl, , (1) . ,
, (2)
r , , .
. 36 , dl =(rda /cosa). dl (2), .
a 1 a 2, , , :
.
a 2 =a 1 .
,
.
,
|
|
.
,
,
j =990 .
16. v =1,83×106 / , . U , Ei =13,6 ? ( , .)
. U, W , , , Ei, . . W+ =Ei. W=eU =(mv2 /2), eU +(mv2 /2)= Ei.
.
- () , , , , 1 . 1 =1,610-19 .
( ; , ):
.
17. , , r min, , .
. , . ( ), ( ). . ‑ , . .
. , , , . . , , . . .
, , . .
,
- ; - .
.
, , , ( =0). , , . .
= . (1)
, , , , . .
= . (2)
(1) (2),
= . (3)
:
(4)
Q 1 Q 2, , , r - . ,
(5)
(4) (5) (3)
( ), /.
18. U 0 = 10 , U l=100 , , (. 37). d 2 . l 1 , 20 c. , l 2=1 .
. : 1) , U 0, ; 2) . , .
|
|
. 37 , | BC|=h 1 +h 2, h 1 - , ; h 2- D , , υ 0, , .
h 1 h 2. ,
. (1)
- , ; t - .
a=F/m, F - , ; - . , F =eE=eU 1 /d, ; U 1 - ; d - . ,
l 1- . , , : .
(2)
(1) , F, t ,
h 2 MDC :
, (3)
- ; l 2 - .
=at, , F t
.
(3), , (3),
| BC |
| BC|=
U 1, U 0, d, l 1 l 2 , | BC |=5,5c.
19. = 2 = 30/. =60˚ . β=30.
. (. 38, ) β= 30º = π/6 : α1 =α0 β = π/3 π/6 = π/6(. 38, ), α2 = α0 + β= π/3 + π/6 = π/2 (. 38, ).
. , . , , , .
, , : 1) ; 2) .
1- . α
dA=Md =pE sin d ,
,
(1)
,
.
2- . Δ A =Δ = , . = cos ,
|
|
(2)
(1), .
20. : d 1 = 2 d 2 = 1,5 , S 100 2.
. , , C=Q/U, Q - ; U - . U U 1 +U 2 ,
C=Q/ (U 1 +U 2). (1)