Careful measurement of the electric field at the surface of a black box indicates that the net outwa

Question

Careful measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is $8.0 	imes 10^3	ext{ N m}^2	ext{/C}$. What is the net charge inside the box?

Professor PC Thomas Classes · Answer

By Gauss's law, $Q = \epsilon_0 \Phi = 8.854 	imes 10^{-12} 	imes 8.0 	imes 10^3 = 70.83 	imes 10^{-9}	ext{ C} \approx 0.07\mu C$.