$A$ hollow sphere of charge does not produce an electric field at any

What is the flux through a cube of side $a$ if a point charge of $q$ is at one of its corners?

Mention applications of Gauss's law.

Consider a solid insulating sphere of radius $R$ with charge density varying as $\rho = \rho_0 r^2$,where $\rho_0$ is a constant and $r$ is measured from the centre. Consider two points $A$ and $B$ at distances $x$ and $y$ respectively $(x < R, y > R)$ from the centre. If the magnitudes of the electric fields at points $A$ and $B$ are equal,then:

If $q$ is the charge per unit area on the surface of a conductor,then the electric field intensity at a point on the surface is

Two concentric conducting thin spherical shells $A$ and $B$ having radii $r_A$ and $r_B$ $(r_B > r_A)$ are charged to $Q_A$ and $-Q_B$ $(|Q_B| > |Q_A|)$. The electric field along a line passing through the centre is: