0
23.264. him = V 2F11in/RonR.
3.265. P = v2B2d2RI(R
pd/S)2; when R = pd/S, the power
is P = P max = 114v2B 2dS1p.
3.266. U = 1/4110/2/n2R2ne = 2pV.
3.267. n = jBleE = 2.5.1028 m--1; almost 1 : 1.
3.268. u0 = 1/1B = 3.2.10-3 m2/(V•s).
3.269. (a) F = 0; (b) F = (110/4n) 2/pm/r2, F1 -
1. B; (c) F
= (p,0/4n) 2Ip,,Ir2, F r.
3.270. F = (R0 l4n) 6nR2Ipmxl(R2 + x2)512.
3.271. F = 312R0PimP2,1n14 = 9 nN.
3.272.
2Bx3/R9R2 = 0.5 kA.
3.273. B' =B R2 sine
cos2 a.
3.274. (a) %, H dS = nR2B cos 9
1)/N-10;
(b) ic;IB dr = (1— [) B1 sin O.
3.275. (a) Isu,. =
(b) 1;ot = xI; in opposite directions.
3.276. See Fig. 24.
3.277. B —
R0111R2 I
111+14 nr •
3.278. B = 2B0[11(1
3.279. B = 3B9[t/(2
3.280. H, = NIll = 6 kA/m.
3.281.
H
bBliuond =
=0.10 kA/m.
3.282. When b << R, the permeability is 12
2aRBI(p,0NI
bB) = 3.7-103.
3.283. H = 0.06 kA/m, Rmax z 1.0.104.
3.284. From the theorem on circulation of the vector H we
obtain
B
tio N I
11°3-cd H = 1.51 — 0.987H (kA/m).
b
Besides, B and H are interrelated as shown in Fig. 3.76. The required values of H and B must simultaneously satisfy both relations.
Solving this system of equations by means of plotting, we obtain
H z 0.26 kA/m, B z 1.25 T, and p, = B/R0H z 4.103.
3.285. F z 112xSB21110 •
3.286. (a) xn, = 1/ V 47i; (b) X = RoFmax V e/a/VB 3.6.10-4.
3.287. A
1/2xVB2/R 0•
3.288. e1= By178wIa.
3.289. I = Byll(R
111 ,,), where Rp, = M2/(RI. + B2).
3.290. (a) Acp = 112(o2a2mle = 3.0 nV; (b)
1 /2o1Ba2 =
= 20 mV.
c
3.291..c E dr = — 1 /2c0Bd2 = —10 mV.
Fig. 24.
A