dq d-4o2+2) 0s0= Xordz 4o2+z2为 05 =422+2 0 三2 Another way:Gauss'Law 入0 个N Gaussian Surface [eoE.da=eoE,2πrl=oL Er= 10 2or 6.641,Electromagnetic Fields,Forces,and Motion Lecture 3 Prof.Markus Zahn Page 8 of 126.641, Electromagnetic Fields, Forces, and Motion Lecture 3 Prof. Markus Zahn Page 8 of 12 ( ) ( ) 0 r 2 2 3 2 2 2 0 0 dq rdz dE cos 4 rz 4 rz λ = θ = π + π + ε ε ( ) 0 r r 3 0 2 2 2 z z r dz E dE 4 r z +∞ +∞ = −∞ = −∞ λ = = π + ε ∫ ∫ ( ) 0 1 0 22 2 2 z r z 4 rz r +∞ =−∞ λ = π + ε 0 2 r0 λ = πε Another way: Gauss’ Law ε ε = π =λ ∫ i 0 0 r S E da E 2 rL L 0 λ = πε 0 r 0 E 2 r