A closed surface that does not contain any net charge will have zero net flux because the number of electric field lines entering the surface equals the number of lines exiting it. This concept can be visualized in two dimensions and extends to three dimensions, where field lines from an external charge enter and exit the closed surface equally. When a surface encloses a charge, only the outgoing field lines contribute to the net flux, resulting in a non-zero value. The principle relies on the conservation of electric field lines, ensuring that any incoming lines are balanced by outgoing lines. Understanding this balance clarifies why the net flux remains zero for surfaces without enclosed charges.
