Two point charges of $ + 2\,\mu C$ and $ + 6\,\mu C$ repel each other with a force of $12\, N$. If each is given an additional charge of $ - 4\,\mu C$, then force will become

In the figure a potential of $+1200\, V$ is given to point $A$ and point $B$ is earthed, what is the potential at the point $P$ ?......$V$

Four charges equal to $-Q$ are placed at the four corners of a square and a charge $q$ is at its centre. If the system is in equilibrium, the value of $q$ is

A square plate of side $'a'$ is placed in $xy$ plane having centre at origin if charge density of square plate is $\sigma = xy$ then. Total charge on the plate will be.

Two charges $+q$ and $-3q$ are placed on $x-$ axis separated by a distance $d$. ($-3q$ is right of $q$) Where should a third charge $2q$ be placed such that it will not experience any force ?

If on the concentric hollow spheres of radii $r$ and $R( > r)$ the charge $Q$ is distributed such that their surface densities are same then the potential at their common centre is