A charge 'Q' C is placed at the centre of a cube. The electric flux through two opposite faces of the cube is
($\epsilon_0$ = permittivity of free space)

The capacitance of a capacitor becomes $\dfrac{7}{6}$ times the original value if dielectric slab of thickness $t = \dfrac{2d}{3}$ is introduced between the plates, where 'd' is the distance of separation between the plates. The dielectric constant of the slab is

Two identical parallel plate air capacitors are connected in series to a battery of e.m.f. 'V'. If one of the capacitor is inserted in liquid of dielectric constant 'K' then potential difference of the other capacitor will become

A condenser of capacity $C_1$ is charged to potential $V_1$ and then disconnected. Uncharged capacitor of capacity $C_2$ is connected in parallel with $C_1$. The resultant potential $V_2$ is