The number of field lines crossing a given area is given by the electric flux. For a closed surface (like a cube or sphere) the total electric flux is given by Gauss's law:
Electric flux through a closed surface = Q/ε₀, (1)
where Q is the net charge inside the closed surface. A point charge Q = 24q is placed somewhere inside a cube. The electric flux through the bottom surface of the cube is measured to be φ = 3.98q/ε₀. What is the approximate location of the charge?
a) Slightly off center.
b) Slightly off center, towards the top surface.
c) Slightly off center, towards the bottom surface.
d) Far from the center, closer to the bottom surface.
e) At the center of the cube.