Four charges,each of value $Q = \frac{10}{3} \times 10^{-9} \ C$,are placed at the four corners of a square of side $a = 8 \ cm$. What is the electric potential at the center of the square?

An electron enters a high potential region $V_2$ from a lower potential region $V_1$. What happens to its velocity?

$A$ hollow conducting sphere of radius $R$ has a charge $(+Q)$ on its surface. What is the electric potential within the sphere at a distance $r = \frac{R}{3}$ from its centre?

At the centre of a half ring of radius $R=10 \ cm$ and linear charge density $\lambda = 4 \ nC \ m^{-1}$,the potential is $x \pi \ V$. The value of $x$ is . . . . .

Draw a graph of $V$ versus $r$ for a uniformly charged spherical shell of radius $R$.

Along the $x$-axis,three charges $\frac{q}{2}, -q$ and $\frac{q}{2}$ are placed at $x=0, x=a$ and $x=2a$ respectively. The resultant electric potential at a point $P$ located at a distance $r$ from the charge $-q$ $(r > a)$ is ($\varepsilon_0$ is the permittivity of free space):