일반물리학 2 — Gauss' Law: Problem 19

19 A long, straight wire has fixed negative charge with a linear charge density of magnitude \(5.2 \text{ nC/m}\). The wire is to be enclosed by a coaxial, thin-walled nonconducting cylindrical shell of radius \(1.2 \text{ cm}\). The shell is to have positive charge on its outside surface with a surface charge density \(\sigma\) that makes the net external electric field zero. Calculate \(\sigma\).