Thread: Electric Field of Earth

need alittle help on this problem.

in a particular region of the earth's atmosphere, the electric field above the earth's surface has been measured to be 152.5 N/C downward at an altitude of 254 m, and 173.5 N/C downward at an altitude of 420 m. the permitivity of free space is 8.85X10^(-12) C^2/N*m^2.

neglecting the curvature of the earth, calculate the volume charge density of the atmosphere assuming it to be uniform between 254 m and 420 m. Answer in units of C/m^3.

any hints?

forget it... question needed answered online and time is up, answers posted with it... thanks for the help