The electric field due to a point charge at a distance $6 \mathrm{m}$ from it is $630 \mathrm{N}\hspace{0.17em}{\mathrm{C}}^{-1}$. The magnitude of the charge is

$S_1,S_2,S_3$ are three concentric spherical shells, as shown in figure. $S_1$ and $S_2$ have charge $4 Q$ and $8 Q$ respectively, whereas $S_3$ is uncharged. Find the ratio of the flux passing through $S_1$ to that through $S_3$

The flux through the hemispherical surface in the figure shown below is

A point charge $q$ of mass $m$ is placed at $A$ in external electric field $E$. What will be the acceleration $\text{'}a\text{'}$ of charge particle?