$A$ small conducting sphere is hung by an insulating thread between the plates of a parallel plate capacitor as shown in the figure. The net force on the sphere is

Two insulated charged spheres of radii $20\,cm$ and $25\,cm$ respectively and having an equal charge $Q$ are connected by a copper wire,then they are separated.

Two insulated charged conducting spheres of radii $20\,cm$ and $15\,cm$ respectively and having an equal charge of $10\,C$ are connected by a copper wire and then they are separated. Then

Two spherical conductors $A$ and $B$ of radii $R_1$ and $R_2$ are charged to the same potential and placed at a distance $d$ apart. If these spheres are connected by a conducting wire,what is the ratio of the magnitudes of the electric fields at the surfaces of $A$ and $B$ in the equilibrium state?

Five identical conducting plates,each of face area $A$,are placed parallel to each other with a separation of $d$ between two adjacent plates as shown in the figure. The plates $M$ and $N$ are given charges $Q_1$ and $Q_2$ respectively and the remaining plates are neutral. If the outermost plates are grounded,the potential difference between the plates $M$ and $N$ is . . . . . .

Conduction electrons are almost uniformly distributed within a conducting plate. When placed in an electrostatic field $\overrightarrow{E}$,the electric field within the plate