Electric charges $+q$ and $-q$ are placed at points $A$ and $B$ respectively,which are at a distance of $2L$ apart. If $C$ is the midpoint between $A$ and $B$,then the work done in moving a charge $+Q$ along the semi-circle $CRD$ is

Three particles,each having a charge of $10\,\mu C$,are placed at the corners of an equilateral triangle of side $10\,cm$. The electrostatic potential energy of the system is.....$J$ (Given $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9\,N\cdot m^2/C^2$).

Four identical charges $+50\,\mu C$ each are placed,one at each corner of a square of side $2\,m$. How much external energy is required to bring another charge of $+50\,\mu C$ from infinity to the centre of the square? (Given $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9\,\frac{N\cdot m^2}{C^2}$)

If the electric potential at a point on the surface of a hollow conducting sphere of radius $R$ is $V$,then the electric potential at a point which is at distance $\frac{R}{3}$ from the centre of the sphere is

A charge $+q$ is fixed at each of the points $x = x_0, x = 3x_0, x = 5x_0, \dots, \infty$ on the $x$-axis, and a charge $-q$ is fixed at each of the points $x = 2x_0, x = 4x_0, x = 6x_0, \dots, \infty$. Here $x_0$ is a positive constant. Take the electric potential at a point due to a charge $Q$ at a distance $r$ from it to be $Q/(4\pi\varepsilon_0 r)$. Then, the potential at the origin due to the above system of charges is:

The variation of electrostatic potential $V$ with radial distance $r$ from the centre of a positively charged metallic thin shell of radius $R$ is given by the graph: