In fair weather, over flat ground, there may be a downward electric field of 125 N/C.
(a) Assume that the Earth is a conducting sphere with charge on its surface. If the electric field just outside is 125 N/C pointing radially inward, calculate the total charge on the Earth and the charge per unit area.
______ C
______ nC/m2
(b) At an altitude of 220 m above the Earth's surface, the field is only 95 N/C. Calculate the charge density of the air (assumed constant). [Hint: See the Conceptual Example within the chapter that discusses "Field Lines for a Thin Spherical Shell".]
______ C/m3