Q 1.16: What is the net flux of the uniform electric field of Exercise 1.15 through a cube of side 20 cm oriented so that its faces are parallel to the coordinate planes?
The net flux of the uniform electric field through a cube oriented so that its faces are parallel to the coordinate planes is zero.
This is because the number of lines entering the cube is the same as the number of lines leaving the cube.
Alternatively,
Using Gauss’s law, we know that the flux of electric field through any closed surface S is times the total charge enclosed by S.
i.e.
where, q = net charge enclosed and = permittivity of free space (constant)
Since there is no charge enclosed in the cube, hence .
Zero because the number of field lines entering the cube is the same as the number of field lines leaving the cube.