The work done to assemble the three charges in a configuration as shown in the figure is

Two charges $q_1$ and $q_2$ are fixed at points $A$ and $B$ respectively, separated by a distance of $30 \text{ cm}$. $A$ third charge $q_3$ is moved along a circular path of radius $40 \text{ cm}$ from point $C$ to point $D$. If the difference in potential energy due to the movement of $q_3$ from $C$ to $D$ is $q_3 K / (4 \pi \epsilon_0)$, find the value of $K$. (Given: $AC = 40 \text{ cm}$, $AB = 30 \text{ cm}$, $AD = 40 \text{ cm}$)

Two hollow conducting spheres of radii $R_{1}$ and $R_{2}$ $(R_{1} >> R_{2})$ have equal charges. The potential would be:

Four point charges each $+q$ are placed on the circumference of a circle of diameter $2d$ in such a way that they form a square. The potential at the centre is proportional to

Point charges $q_1 = 2\,\mu C$ and $q_2 = -1\,\mu C$ are kept at points $x = 0$ and $x = 6$ respectively. Electrical potential will be zero at points

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 $x=a+r$ (if $a << r$) is: ($\varepsilon_0$ is the permittivity of free space)