Two parallel metal plates having charges $+ Q$ and $-Q$ face each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will

The work done in placing a charge of $8 \times 10^{-18}$ coulomb on a condenser of capacity $100\, micro-farad$ is

Electric charges $q, q, -2\,q$ are placed at the comers of an equilateral triangle $ABC$ of  side $l$. The magnitude of electric dipole moment of the system is

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

A sphere of radius $R$ and charge $Q$ is placed inside an imaginary sphere of radius $2R$ whose centre coincides with the given sphere. The flux related to imaginary sphere is

A solid coducting sphere having a charge $Q$ is surrounded by an uncharged concentric  conducting hollow spherical shell. Let the potential difference between the surface of the  solid sphere and that of the outer surface of the hollow shell be $V$. If the shell is now  given a charge $-3Q$, the new potential difference between the same two surface is :-........$V$