Three identical small electric dipoles are arranged parallel to each other at equal separation a as shown in the figure. Their total interaction energy is $U$. Now one of the end dipole is gradually reversed, how much work is done by the electric forces.

There are two equipotential surface as shown in figure. The distance between them is $r$. The charge of $-q\,$ coulomb is taken from the surface $A$ to $B$, the resultant work done will be

A point charge $2 \times 10^{-2}\,C$ is moved from $P$ to $S$ in a uniform electric field of $30\,NC ^{-1}$ directed along positive $x$-axis. If coordinates of $P$ and $S$ are $(1,2$, $0) m$ and $(0,0,0) m$ respectively, the work done by electric field will be $.........\,mJ$

Obtain the equation of electric potential energy of a system of two electric charges in external electric field.

A particle of mass $100\, gm$ and charge $2\, \mu C$ is released from a distance of $50\, cm$  from a fixed charge of $5\, \mu C$. Find the speed of the particle when its distance  from the  fixed charge becomes $3\, m$. Neglect any other force........$m/s$

A square of side ‘$a$’ has charge $Q$ at its centre and charge ‘$q$’ at one of the corners. The work required to be done in moving the charge ‘$q$’ from the corner to the diagonally opposite corner is