, , q1, q2, q3,... qn, p:
n
E = E 1+ E 2 +... + E n = S E i. (1.11)
i = 1
p p p () . p p p.
p , p q1 , E 1, q2 E 2(p 1.5). E (1.11)
E = E 1 + E 2 . (1.12)
2 = E12 + E22 - 2 E1E2cosa, (1.13)
a - , .
+ q 1h
2 1 l E A E+
- q 2ha +q h h- q h
r
.1.5 .1.6
p (1.9) (1.12) p p. pp pp , .
pp. , p p p, p p p l, p r pp (p. 1.6).
= q l, (1.14)
l - , , .
pp (p.1.6), p p
= + + -, (1.15)
p (1.9), ,
q q q r l
E = ¾¾¾¾¾¾ - ¾¾¾¾¾¾ = ¾¾¾¾¾¾.
4pee0(r - l /2)2 4pee0(r + l /2)2 2pee0(r2- l 2/4)2
l << r, l 2/4 .
:
l
E = ¾¾¾¾¾. (1.16)
2pee0r3
H p , p pp, p p p (p.1.7).
E+ = E- p +q - q , (1.15) p :
E = E+ cosa + E - cos a = 2E+ cosa = 2q/(4pee0r2). (1.17)
l
+q a - q
r d r
E -
-
a E
E + .1.7
a - p E + E.
H p. 1.7
------¾Ø l
r = Ö d2 + l 2 / 4, cos a = ¾¾¾¾. (1.18)
------- ¾Ø
2 Ö d2 + l 2/4
(1.18) p (1.17),
2q l 2q l
E = ¾¾¾¾¾¾ . ¾¾¾¾¾Ø = ¾¾¾¾¾¾¾.
4pee0(d2 + l 2/4) 2Öd2 + l 2/4 8pee0 (d2 + l 2/4)3/2
|
|
l 2/4 << d2, :
2q l q l p
E ¾¾¾¾¾¾ = ¾¾¾¾ = ¾¾¾¾. (1.19)
8pee0 (d2)3/2 4pee0 d3 4pee0 d3
p p p p . p q p p dq, p .
p dq pp p dV, p ds, dl. p p p r = dq/dV, p s = dq/ds, p t = dq/dl. p p /3, /2, /.
p , pp- p, p
dq
d= ¾¾¾¾. (1.20)
4pe0r2
Hp d E , p dq, p , d E :
E = ò d E. (1.21)
F .
pp. H p l = 10 pp pp p t = 10-8 / (p 1.8). H p p p b = 20 p q = 5 . p , p p p, .
l b
q F
dr r
. 1.8
. (1.3,) p p . p dr p dq1 = tdr, p pp . p dq1 q p
q dq1 qtdr
dF = ------------ = ------------, (1.22)
4pee0r2 4pee0r2
q
l +b
F = ∫ dF,
l
r - dr q.
pp p,
b + lb + l
qt dr qt qt
F = -------- ∫ ---- = - --------- │ = ---------------------- =
4pee0 b r2 4pee0 r b 4pee0(1/b -1/b+ l)
qt l
= -----------------.
4pee0 b (b+ l)
:
l = 10-1, b = 210-1, q = 510-9 , t = 10-6 / ,
e = 1, 1/4pe0= 9 .109 H.2/2.
F = 510-910-610-19 109/ 210-1 (10-1 + 210-1) = 7,510-5().
F . 1.8. (1.7):
= F/q = 7,510-5/ 510-9 = 1,25104 (/ ).
F.
pp. p q pp pp p R. p p p , , p h p (p. 1.9).
. d l, p dq = t d l, t - p .
d E : d E 1, ( ), d E 2, , ..
d E = d E 1 + d E 2.
|
|
dl ¢
d E
d E 2 d E 1 h
d E 2 ¢ a R
d E¢ r d l
.1.9
E = ∫d E = ∫d E 1 + ∫d E 2,
L L L
. , d l d l ¢, , d E 2 d E 2¢ :
d E 2 = - d E 2¢.
∫d E 2 = 0 E = ∫d E = ∫d E 1.
L L L
d E 1 e , E . , , E, ,
2πR 2πR cosadq 2πR thd l
E = ∫ dE1 = ∫ --------- = ∫ --------.
L 0 4pee0r2 0 4pee0r3
, r d l
r = (R2 + h2) 1/ 2,
:
2πR thd l t l h 2πR
E = ∫ ----------------- = --------------------│ =
0 4pee0(R2+h2)3/2 4pee0(R2 + h2)3/2 0
Rth
= ---------------------.
2ee0(R2 + h2)3/2
1.4. p p
p
p dS p-p . dS
d = E . dS. (1.23)
p pp dS, p- p E,
d = E . dS . cosa = EndS, (1.24)
En - p p p p n , a.- n (.1.9,). p dS, p p dS, p p n (.1.9,), .. dS = n dS,
d = (EdS) = dS . cosa. (1.25)
dS dS dS
N E n
n a
E dS
.1.9
p p p p dSi.
= ò EdS (1.26)
S
( ).