A solid uncharged conducting sphere has radius $3a$ contains a hollowed spherical region of radius $2a$. A point charge $+Q$ is placed at a position a distance a from the common center of the spheres. What is the magnitude of the electric field at the position $r = 4a$ from the center of the spheres as marked in the figure by $P?$ $\left( {k = \frac{1}{{4\pi { \in _0}}}} \right)$
$0$
$\frac{kQ}{16a^2}$
$\frac{3kQ}{16a^2}$
$\frac{kQ}{9a^2}$
A solid conducting sphere has cavity, as shown in figure. A charge $+ {q_1}$ is situated away from the centre. A charge $+q_2$ is situated outside the sphere then true statement is
‘At the surface of a charged conductor electrostatic field must be normal to the surface at every point’. Explain.
Two concentric hollow conducting spheres of radius $r$ and $R$ are shown. The charge on outer shell is $Q$. What charge should be given to inner sphere so that the potential at any point $P$ outside the outer sphere is zero?
A thin-walled, spherical conducting shell $S$ of radius $R$ is given charge $Q$. The same amount of charge is also placed at its centre $C. $ Which of the following statements are correct ?
Two spheres of radius $R$ and $2R$ having charge $Q$ and $2Q$ respectively are placed far away from each other. How much charge will flow when key $'k'$ is pressed ?