1. The problem statement, all variables and given/known data Find the magnitude of the electric field intensity at a distance 0.15m from the axis of a long, straight conductor, which has radius 0.03m, and a charge density of 4.0 C/m. 2. Relevant equations Eflux = E.A Eflux = q/e0 q = sigma*h 3. The attempt at a solution Eflux = E*Area Thus, Eflux = E*2pi*r*h (Surface area of the gaussian cylinder we superimpose over the conductor) Also, Eflux = q/e0 -> where e0 is the permittivity of free space and q is the enclosed charge in the gaussian surface. q = sigma*h Therefore we substitute for the q, and equate the two Eflux equations to get: Eflux = E*2pi*r*h = sigma*h/e0 Solve for E and we get: E = sigma/(2pi*r*e0) Now we substitute the given values: 4/(2pi*(0.03)*(8.85*10^-12)) = 2.40*E12 or 2.40*10^12 N/C I have no idea how to find the electric field at the distance 0.15m away from the surface. Please help! I would need the value of q to do this, however this is not a point charge we're dealing with but a surface charge, so I'm a bit lost.