If more field lines leave a closed surface than enter that surface, then
A) a net positive charge is contained inside the surface.
B) a net negative charge is contained inside the surface.
C) an error has been made since the number of field lines entering a surface must equal those leaving the surface.
D) an operating electron gun is inside the surface.
E) there must be a charge on the surface.

Question

Quizplus · Accepted Answer

According to Gauss's law, the total electric flux through a closed surface is proportional to the net charge contained inside that surface. If more field lines leave the surface than enter, then the flux through the surface is positive and there must be a net positive charge inside the surface.

If More Field Lines Leave a Closed Surface Than Enter