spherical portion has been removed from a solid sphere having a charge distributed uniformly in its volume as shown in the figure. The electric field inside the emptied space is : 

Consider a system of three charges $\frac{q}{3}, \frac{q}{3}$ and $-\frac{2q}{3}$ placed at points $A, B$ and $C$, respectively, as shown in the figure. Take $O$ to be the centre of the circle of radius $R$ and angle $CAB= {60}^{°}$.

STATEMENT-$1$: For practical purposes, the earth is used as a reference at zero potential in electrical circuits. 

and
STATEMENT$-2$: The electrical potential of a sphere of radius $R$ with charge $Q$ uniformly distributed on the surface is given by $\frac{Q}{4{\mathrm{\pi \epsilon }}_{0}R}$.

A disk of radius $\frac{a}{4}$ having a uniformly distributed charge $6\mathrm{C}$ is placed in the x-y plane with its centre at $(–\frac{a}{2}, 0, 0).$A rod of length a carrying a uniformly distributed charge $8\mathrm{C}$ is placed on the x-axis from $x=\frac{a}{4}\text{ to} x=\frac{5a}{4}$ Two point charges $-7\mathrm{C}$ and $3\mathrm{C}$ are placed at $(\frac{a}{4}, –\frac{a}{4}, 0)$ and $(–\frac{3a}{4}, \frac{3a}{4}, 0),$ respectively. Consider a cubical surface formed by six surfaces $x=\pm \frac{a}{4}, y=\pm \frac{a}{4}, z=\pm \frac{a}{4}.$ The electric flux through this cubical surface is 

A few electric field lines for a system of two charges $Q_1$ and $Q_2$ fixed at two different points on the $x$-axis are shown in the figure. These lines suggest that

A uniformly charged thin spherical shell of radius $R$ carries uniform surface charge density of $\sigma$ per unit area. It is made of two hemispherical shells, held together by pressing them with force $F$ (see figure). $F$ is proportional to