20

t da

r1 r R r2

a1 a2

dl

r*dr

a a

dl

dl = (r*dr)/sina

r = R/sina

dl = (R*da)/sin2a

dE = t*dl/(4pe0r2)

dEx = dE cosa = [t*dl/(4pe0r2)]*cosa= = [(tRda*sin2a)/(sin2a*4pe0R2)]*cosa = = [t/(4pe0R)]*cosa*da;

dEy = dE sina = [t/(4pe0R)]*sina*da;

Ex = [t/(4pe0R)]*a1òa2cosada = = [t/(4pe0R)]*(sina2 - sina1);

Ey = [t/(4pe0R)]*a1òa2sinada = = [t/(4pe0R)]*(cosa1 - cosa2);

E = ÖE2x + E2y;

:

a1 = 0; a2 = 180;

Ex = 0; Ey = t/(2pe0R).

10. :

Ex dx Ex+(Ex/x)dx

dz

dy

Z

= [Ex + (Ex/x)dx]dydz cos 0 + + EX dydz cos180;

X = (Ex/x)dxdydz = (Ex/x)dV;

= (E/y)dxdydz;

Z = (EZ/z)dxdydz;

oSòEdS = + + Z = (Ex/x + + E/y + EZ/z)dV;

lim [(oSòEdS)/V] = div E

V 0

div E = (Ex/x + E/y + EZ/z)

:

oSòEdS = q/e0e = (VòrdV)/(e0e);

divE = r/(e0e);

divD = r.

24. :

+ + + + + + + + + + + + + + + +

- -

+ +

+ - - -

+ +

¾ ¾ ¾ ¾ ¾ ¾ ¾ ¾ ¾

E = E0 E

E0/e = E0 - E

E = E0 (1 1/e) = E0 [(e - 1)/e]

e - 1 = c - ;

= 0*(c/e);

= s/e0;

0 = s/e0;

s = s*(c/e), s ;

s - .

47. :

PM B

a

u N

a

dM=Ndt

M

Msina

r

I

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