A uniformly charged conducting sphere is having radius $1 \mathrm{m}$ and surface charge density $20 \mathrm{C} {\mathrm{m}}^{-2}$. The total flux leaving the Gaussian surface enclosing the sphere 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?