$A$ conducting sphere of radius $10 \; cm$ has an unknown charge. If the electric field $20 \; cm$ from the centre of the sphere is $1.5 \times 10^{3} \; N/C$ and points radially inward,what is the net charge (in $nC$) on the sphere?

$A$ charge of $1 \mu C$ each is placed on five corners of a regular hexagon of side $1 \ m$. The electric field at its centre is . . . . . . $N$/$C$.

The electric field at a place is given by $\overrightarrow{E} = E_0 \hat{i} \text{ V/m}$. $A$ particle of charge $+q_0$ moves from point $A(0, a)$ to point $B(a, 0)$ along a circular path as shown in the figure. Find the work done by the electric field in this motion.

Electric field strength due to a point charge of $5\,\mu C$ at a distance of $80\, cm$ from the charge is:

Four equal charges of value $+Q$ are placed at four vertices of a regular hexagon of side $a$. By suitably choosing the vertices, what can be the maximum possible magnitude of the electric field at the centre of the hexagon?

Two equal positive point charges are separated by a distance $2a$. The distance of a point from the centre of the line joining two charges on the equatorial line (perpendicular bisector) at which the force experienced by a test charge $q_0$ becomes maximum is $\frac{a}{\sqrt{x}}$. The value of $x$ is $................$