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
${\left( {\frac{{{q^2}L}}{{2\pi {\varepsilon _0}mg}}} \right)^{\frac{1}{3}}}$
${\left( {\frac{{q{L^2}}}{{2\pi {\varepsilon _0}mg}}} \right)^{\frac{1}{3}}}$
${\left( {\frac{{{q^2}{L^2}}}{{4\pi {\varepsilon _0}mg}}} \right)^{\frac{1}{3}}}$
${\left( {\frac{{{q^2}L}}{{4\pi {\varepsilon _0}mg}}} \right)^{\frac{1}{3}}}$
Six charges are placed at the corner of a regular hexagon as shown. If an electron is placed at its centre $O$, force on it will be:
A $10\,\mu C$ charge is divided into two parts and placed at $1\,cm$ distance so that the repulsive force between them is maximum. The charges of the two parts are :
Two free positive charges $4q$ and $q$ are a distance $l$ apart. What charge $Q$ is needed to achieve equilibrium for the entire system and where should it be placed form charge $q$ ?
An electric field due to a positively charged long straight wire at a distance $r$ from it is proportional to $r^{-1}$ in magnitude. Two electrons are orbiting such a long straight wire in circular orbits of radii $1 A$ and $2 A$. The ratio of their respective time periods is
Two identical conducting spheres $A$ and $B,$ carry equal charge. They are separated by a distance much larger than their diameter, and the force between them is $F$ . A third identical conducting sphere, $C,$ is uncharged. Sphere $C$ is first touched to $A,$ then to $B,$ and then removed. As a result, the force between $A$ and $B$ would be equal to