A point charge is placed at the centre of spherical Gaussian surface. Is electric flux `phi_(E)` changed if
(a) The sphere is replaced by a cube of same or different volume ?
(b) The charge is moved off-centre in the original sphere, still remaining inside ?
( c ) The charge is moved just outside the original sphere ?
(d) A second charge is placed near the outside to the origianl schere ?
(e) A second charge is placed inside the Gaussian surface ?

Explanation

For answering all the question keep in your mind that as per Gauss's law the total electric flux oer the surface is just dependent on the net charge enclosed and the flux is independent of the shape or size of the surface.
(a) `phi _(E )` is not changed because the net charge enclosed is same.
(b ) Again `phi_(E)` is not changed because the net charge enclosed is same and the flux is independent of the shape or size of the surface.
(c ) `phi_(E )` is not changed because the charge is still enclosed by the surface. The charge need not charge is enclosed by the surface.
(e ) The flux will not be changed because the new charge is outside the surface and net charge enclosed is still the same.
(f ) The flux now will change because the net charge enclosed has changed.