posted by Amy .
On a clear day, the Earth’s atmospheric electric field near the ground has a magnitude of 100 N/C and points vertically down. Inside the ground, the electric field is zero, since the ground is a conductor. Consider a mathematical box of 1.0 m x 1.0 m x 1.0 m, half below the ground and half above. What is the electric flux through the sides of the box? What is the charge enclosed by the box?
Use Gauss' Law. Assume there is no flux in the downward direction or out the sides. The flux through the top (E* 1 m^2) will be proportional to the charge inside the box. Look up the law for the poprtionality constant.
That charge will reside at the surface, since the groud is a conductor.