Find the electric flux coming out from one race of a cube of edge a, centre of which a point charge q is placed

Explanation

Here the total solid angle subtended by cube surface at the point charge q is `4pi`. As q is at centre of cube, we can say the each face of cube subtend equal solid angle at the centre, thus solid angle subtended by each force at point charge is
`sigma_("face")=(4pi)/(6)` steradian
Thus electric flux through each face is

`phi_("face")=(q//epsilon_(0))/(4pi)xxsigma_("face")`
`=(q//epsilon_(0))/(4pi)xx(4pi)/(6)=(q)/(6in_(0))`