$A$ hollow metal sphere has a radius $r$. The potential difference between a point on its surface and a point at a distance $3r$ from its center is $V$. The electric intensity at the distance $3r$ from the center of the sphere will be

$A$ metal ball of radius $R$ is placed concentrically inside a hollow metal sphere of inner radius $2R$ and outer radius $3R$. The ball is given a charge $+2Q$ and the hollow sphere is given a total charge $-Q$. The electrostatic potential energy of this system is:

Two capacitors of capacitance $C$ and $2C$ are connected in parallel and charged to a potential difference $V$. The battery is then disconnected,and the space between the plates of the capacitors is completely filled with a dielectric material of constant $K$. Determine the new potential difference across the capacitors.

$A$ parallel plate capacitor with a dielectric of dielectric constant $K$ between the plates has a capacitance $C$ and is charged to a potential $V \ volt$. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is

For a hollow spherical shell of radius $R$ carrying a charge $q$,how does the electric potential $(V)$ change with respect to the distance $(s)$ from the centre?

In the given circuit,$C_1=2\,\mu F, C_2=0.2\,\mu F, C_3=2\,\mu F, C_4=4\,\mu F, C_5=2\,\mu F, C_6=2\,\mu F$. The charge stored on capacitor $C_4$ is $.....\mu C$.