What is the excess charge on the surface of the earth?

1. Feb 11, 2008

gallib

1. The problem statement, all variables and given/known data

The earth has a vertical electric field at the surface, pointing down, that averages 117 N/C. This field is maintained by various atmospheric processes, including lightning. What is the excess charge on the surface of the earth?

2. Relevant equations

E=ke*Q/r^2 Q=Er^2/ke

3. The attempt at a solution

I attempted to plug in E = 117, r= radius of the earch, and ke= 8.99*10^9 into the equation to find Q, but this answer was wrong. Any ideas, thanks.

2. Feb 12, 2008

hectoronevu

Why don't you use the formula for Electric flux? The Net electric flux through surface is basically Electric field * (4pi*(radius of earth ^ 2)) = excess charge / permittivity constant.

3. Feb 12, 2008

gallib

Ah..thank you.

Last edited: Feb 12, 2008
4. Feb 12, 2008

hectoronevu

Yeah, permittivity constant is 8.85*10^-12.