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 ?

Two charged conducting spheres of radii $a$ and $b$ are connected to each other by a wire. What is the ratio of electric fields at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of a conductor is higher than on its flatter portions.

‘At the surface of a charged conductor electrostatic field must be normal to the surface at every point’. Explain.

Electric potential of earth is taken to be zero because earth is a good

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 $P?$ $\left( {k = \frac{1}{{4\pi { \in _0}}}} \right)$

A metallic rod is placed in a uniform electric field. Select the correct option.