3) A long, straight wire has fixed negative charge with a linear charge density of magnitude 3.6 nC/m. The wire is enclosed in a thin, coaxial, nonconducting cylindrical shell of radius 1.5 cm. The shell has a positive charge on its outer surface with a surface charge density o that makes the net external electric field zero. Calculate o. 4) (SKIP for now-try it after you watch my extra lecture video!!) A conducting rod of radius R = 1.30 mm and length L=11.00 m is inside a thin-walled coaxial conducting cylindrical shell of