12. A long, nonconducting cylinder (radius = 6.0 mm) has a nonuniform volume charge density given by αr², where α = 6.2 mC/m⁵ and r is the distance from the axis of the cylinder. What is the magnitude of the electric field at a point 2.0 mm from the axis?
(A) 0.4 N/C
(B) 3.6 N/C
(C) 0.8 N/C
(D) 2.5 N/C
(E) 1.4 N/C

答案：登入後查看
統計： 尚無統計資料