A hollow cylinder has a charge $q$ coulomb within it. If $\phi $ is the electric flux in units of voltmete associated with the curved surface $B$ , the flux linked with the plane surface $A$ in units of volt-meter will be

A charge $q$ is placed at the centre of the line joining two equal charges $Q$. The system of the  three charges will be in equilibrium, if $q$ is equal to

If $\vec E = \frac{{{E_0}x}}{a}\hat i\,\left( {x – mt} \right)$ then flux through the shaded area of a cube is

A parallel plate capacitor is charged to a potential difference of $100\ V$ and disconnected from the source of emf. A slab of dielectric is then inserted between the plates. Which of the following three quantities change?

$(i)$ The potential difference
$(ii)$ The capacitance
$(iii)$ The charge on the plates

Consider a cube of uniform charge density $\rho$. The ratio of electrostatic potential at the centre of the cube to that at one of the corners of the cube is