Two positive point charges of $12\,\mu C$ and $8\,\mu C$ are $10\,cm$ apart. The work done in bringing them $4\, cm$ closer is

Two identical particles of mass m carry a charge $Q$ each. Initially one is at rest on a smooth horizontal plane and the other is projected along the plane directly towards first particle from a large distance with speed $v.$ The closest distance of approach be 

Two charges $-q$ each are separated by distance $2d$. A third charge $+ q$ is kept at mid point $O$. Find potential energy of $+ q$ as a function of small distance $x$ from $O$ due to $-q$ charges. Sketch $P.E.$ $v/s$ $x$ and convince yourself that the charge at $O$ is in an unstable equilibrium.

Identify the $WRONG$ statement

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

The work done in carrying a charge of $5\,\mu \,C$ from a point $A$ to a point $B$ in an electric field is $10\,mJ$. The potential difference $({V_B} - {V_A})$ is then