Question

5. What must be tge charge of an isolated spherical conductor 30.0 cm in diameter to produce an electric field of 150 N/C just outside the surface?

Answer 1

$$E=k\frac{q}{r^2}$$

$$q=\frac{Er^2}{k}=\frac{150*0.15^2}{9*10^9}=3.75*10^{-10}\:\rm C$$