Four closed surfaces $S_1, S_2, S_3$ and $S_4$ together with charges $+q, -q$ and $-2q$ are shown. Through which one of the surfaces is the net flux zero?

Electric field lines of force of a positive point charge are

Electric flux through a surface of area $100 \ m^2$ lying in the $xy$ plane is (in $V-m$) if $\vec E = \hat i + \sqrt 2 \hat j + \sqrt 3 \hat k$.

The $S.I.$ unit of electric flux is

$A$ uniformly charged conducting sphere of diameter $3.5 \ cm$ has a surface charge density of $20 \ \mu C \ m^{-2}$. The total electric flux leaving the surface of the sphere is nearly:
[permittivity of free space,$\epsilon_0 = 8.85 \times 10^{-12} \ SI \ unit$]

$A$ hollow cylinder has a charge $q$ coulomb within it. If $\phi$ is the electric flux in unit of $V-m$ associated with the curved surface $C$, the flux linked with the plane surface $A$ in unit of $V-m$ will be. $[\epsilon_0 = \text{permittivity of free space}]$