Air becomes a conductor when the electric field strength exceeds 3.00 × 106 N/C. Determine the maximum amount of charge that can be carried by a metal sphere 8.5 m in radius. The value of the Coulomb constant is8.99×109 N·m2/C2.

Question

Answer in units of C.
I have the equations E=F/q and F=kq/r^2 but I'm not sure when to use either one.

Answer 1

Neither. We're talking fields not forces.
E = kq/r^2 or rearranged:
q=Er^2/k
Plug 'n' chug.