Re: [理工] [電磁]-雲科90-電資所

[kagato (包)]

※ 引述《aacvbn ( 姿勢+)》之銘言：
: http://www.lib.yuntech.edu.tw/exam_new/90/el.pdf
: 第14頁第2題 有附圖@@
: The insulator between the inner conducting cylinder a and outer
: cylindrical shell b is composed of four sectors of  equal
: dimensions but different dielectric constants,
: ε_1 ε_2 ε_3  and ε_4 ,see Fig.2. The radius of cylinder a is (r_a)
: and the inner radius of outer cylindrical shell b is (r_b).
: In case the cylinders extend indefinitely ,
: find the capacitance per unit length.


令中央帶電+ρ_L , 外圍帶電-ρ_L

由Maxwell-equation  ∫Dds = ρ_L → (D1+D2+D3+D4)*2πr/4 = ρ_L

ε1E+ε2E+ε3E+ε4E = 2ρ_L/πr , E = 2ρ_L/[πr(ε1+ε2+ε3+ε4)]

                   2ρ_L*ln(b/a)
V =  ∫Edr = ____________________
             [π(ε1+ε2+ε3+ε4)]

            π(ε1+ε2+ε3+ε4)
C=ρ_L/V = _____________________   (F/m)
              2ln(b/a)

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 118.171.102.115
推 iyenn: m(_ _)m
→ kagato:i大神手不要拜我~"~
推 iyenn:我常算錯,要多拜一些神佛:)
推 QQkimi:慘! i大榜首位置不保了 m(_ _)m
→ iyenn:我只要榜尾:(
推 youmehim:還好不關我的事了   ╮(￣▽￣)╭
推 doom8199:m(_ _)m
推 iyenn:   最近在逃避現實     ╮(￣▽￣)╭