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
only $(i)$ and $(ii)$
only $(i)$ and $(iii)$
only $(ii)$ and $(iii)$
All $(i), (ii)$ and $(iii)$
Three capacitors $1, 2$ and $4\,\mu F$ are connected in series to a $10\, volts$ source. The charge on the plates of middle capacitor is
An electric dipole is situated in an electric field of uniform intensity $E$ whose dipole moment is $p$ and moment of inertia is $I$. If the dipole is displaced slightly from the equilibrium position, then the angular frequency of its oscillations is
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
Two spheres of radius $a$ and $b$ respectively are charged and joined by a wire. The ratio of electric field of the spheres is
Two equal $-ve$ charges $-q$ are fixed at the points $(0, a)$ and $(0, -a)$ on the $y-$ axis. A positive charge $Q$ is released from rest at the point $(2a, 0)$ on the $x-$ axis. The charge will