udy 3. What is the magnitude of the electric field inside a conducting sphere of radius r? Derive an expression for the magnitude of the electric field at a distance a from the center of the sphere (a>r). 4. Problem solving - Flux and Gauss' law Consider an infinitely long, very thin metal tube with radius R-2.90 cm. The above figure shows a section of it. If the linear charge density of the cylinder is =1.50E-8 Cm, what is the approximate magnitude of the electric field at radial distance r=2R? The value of the permittivity constant is s0=8.85E-12 C2N-m2. Save and Close Submit Search