A square surface of side L metre is in the plane of the paper. A uniform electric field E (volt/m), also in the plane of the paper, is limited only to the lower half of the square surface, (see figure). The electric flux in SI units associated with the surface is

Options

A. `EL^(2)//(2 epsilon_(0))`
B. `EL^(2)//2`
C. zero
D. `EL^(2)`

Answer

C

Explanation

Electric flux `(phi_(e))` is a measure of the number of field lines crossing a surface. The numgber of filled lines passing through unit are `(N//S)` will be proportional to the electric field, or
`(N)/(S) prop E rArr N prop ES`
The quantity ES is the electric flux through surface S.
As we have seen in the problem that, lines of force that enter the closed surface leave the surface immediately, so no electric flux is blund to the system. Hence, electric flux is zero.