3.205. (a) I = (V 0IR) e-2tIRC'
(b) Q = 1/4
3.206. elm = lcor/qR = 1.8.1011 C/kg.
3.207. p = lImle = 0.40 RN • s.
3.208. s = enl (v)11, 107 m, where n is the concentration of
free electrons, (v) is the mean velocity of thermal motion of an
electron.
3.209. (a) t = en1SII = 3 Ms; (b) F = enlpl = 1.0 MN,
where p is the resistivity of copper.
3.210. E (I12:-ce0r) ym/2eV=32 V/m, 6,9=(//4neo) V m/2eV =
= 0.80 V.
3.211. (a) p (x)= — 419E0ex-213; (b) j = 4/9E,a3/ 2 V 2e/m.
3.212. n = Idle (u:
ii- ( ;) VS = 2.3.108 cm-3.
3.213. uo = (1)0/2/2Vo.
3.214. (a) ni = I sat IeV = 6.109 cm--3 .s -1; (b) n = V nilr
6.107 cm-3.
3.215. t=
1)/ V rni = 13 ms.
3.216. t = EAU/enid2 = 4.6 days.
3.217. I = ev aead.
3.218. j = (ecui — 1) enila.
3.219. (a) B = µ,I/2R = 6.3 p.T; (b) B = 1A0 R2I12(112
x2)312=
= 2.3 RT.
3.220. B = ntio/ tan (n/n)/2nR, for n
oo B = I.10//2R
3.221. B = 414l/ltd sin 9 = 0.10 mT.
3.222. B = (n — 9 tan 9) Ro//2nR = 28ta.
3.223. (a) B = P 4 ' 91. ( 2n: (1) + b) ) ; (b) B = 43.t 1 (4: + .17 b 2 .
3.224. B
Roh//1-t2Rr, where r is the distance from the cut.
3.225. B = RoIln2R.
3.226. (a) B = (p,0/4n) (nER); (b) B = (p,0/41t) (1 + 3n/2) PR;
(c) B = (p,0/411) (2
n) IIR.
3.227. B= (110 /4n)1y 2/i = 2.01LT.
3.228. (a) B = (110/4n) V4 -I- n2 I1R = 0.30 RT; (b) B = (p.0/4n) X
x 1/2 +2n + n2 PR= 0.34p,T; (c) B = (p.0/4n) V 2 1/R= P.11 ELT.
3.229. (a) B = Ni/2; (b) B = Rot between the planes and
B = 0 outside the planes.
3.230. B=
ttoix inside the plate,
Roid outside the plate.
3.231. In the half-space with the straight wire, B = p,o//2nr,
r is the distance from the wire. In the other half-space B = 0.
3.232. The given integral is equal to Rol.
3.233. B
1/ 2u 0 [Jr] for r-<„,11,
1 /2p,o [jr] R2/rz for
3.234. B = 1/2p.0 UM i.e. field inside the cavity is uniform.
3.235. j (r) = (b I p, 0) (1
a)
(b) Q = 1/4
3.206. elm = lcor/qR = 1.8.1011 C/kg.
3.207. p = lImle = 0.40 RN • s.
3.208. s = enl (v)11, 107 m, where n is the concentration of
free electrons, (v) is the mean velocity of thermal motion of an
electron.
3.209. (a) t = en1SII = 3 Ms; (b) F = enlpl = 1.0 MN,
where p is the resistivity of copper.
3.210. E (I12:-ce0r) ym/2eV=32 V/m, 6,9=(//4neo) V m/2eV =
= 0.80 V.
3.211. (a) p (x)= — 419E0ex-213; (b) j = 4/9E,a3/ 2 V 2e/m.
3.212. n = Idle (u:
ii- ( ;) VS = 2.3.108 cm-3.
3.213. uo = (1)0/2/2Vo.
3.214. (a) ni = I sat IeV = 6.109 cm--3 .s -1; (b) n = V nilr
6.107 cm-3.
3.215. t=
1)/ V rni = 13 ms.
3.216. t = EAU/enid2 = 4.6 days.
3.217. I = ev aead.
3.218. j = (ecui — 1) enila.
3.219. (a) B = µ,I/2R = 6.3 p.T; (b) B = 1A0 R2I12(112
x2)312=
= 2.3 RT.
3.220. B = ntio/ tan (n/n)/2nR, for n
oo B = I.10//2R
3.221. B = 414l/ltd sin 9 = 0.10 mT.
3.222. B = (n — 9 tan 9) Ro//2nR = 28ta.
3.223. (a) B = P 4 ' 91. ( 2n: (1) + b) ) ; (b) B = 43.t 1 (4: + .17 b 2 .
3.224. B
Roh//1-t2Rr, where r is the distance from the cut.
3.225. B = RoIln2R.
3.226. (a) B = (p,0/4n) (nER); (b) B = (p,0/41t) (1 + 3n/2) PR;
(c) B = (p,0/411) (2
n) IIR.
3.227. B= (110 /4n)1y 2/i = 2.01LT.
3.228. (a) B = (110/4n) V4 -I- n2 I1R = 0.30 RT; (b) B = (p.0/4n) X
x 1/2 +2n + n2 PR= 0.34p,T; (c) B = (p.0/4n) V 2 1/R= P.11 ELT.
3.229. (a) B = Ni/2; (b) B = Rot between the planes and
B = 0 outside the planes.
3.230. B=
ttoix inside the plate,
Roid outside the plate.
3.231. In the half-space with the straight wire, B = p,o//2nr,
r is the distance from the wire. In the other half-space B = 0.
3.232. The given integral is equal to Rol.
3.233. B
1/ 2u 0 [Jr] for r-<„,11,
1 /2p,o [jr] R2/rz for
3.234. B = 1/2p.0 UM i.e. field inside the cavity is uniform.
3.235. j (r) = (b I p, 0) (1
a)