Two point charges $Q$ each are placed at a distance $d$ apart. A third point charge $q$ is placed at a distance $x$ from mid-point on the perpendicular bisector. The value of $x$ at which charge $q$ will experience the maximum $Coulomb's force$ is ...............

There are two metallic spheres of same radii but one is solid and the other is hollow, then

Consider the charges $q, q$, and $-q$ placed at the vertices of an equilateral triangle, as shown in Figure. What is the force on each charge?

Check that the ratio $ke ^{2} / G m _{ e } m _{ p }$ is dimensionless. Look up a Table of Physical Constants and determine the value of this ratio. What does the ratio signify?

In general, metallic ropes are suspended on the carriers which take inflammable material. The reason is

In the given figure two tiny conducting balls of identical mass $m$ and identical charge $q$ hang from non-conducting threads of equal length $L$. Assume that $\theta$ is so small that $\tan \theta \approx \sin \theta $, then for equilibrium $x$ is equal to