Two metal spheres have their radii in the ratio of $4:7$. They are put in contact and a charge $8.8 \times 10^{-7} \text{ C}$ is given to the system. Then they are separated so that each can exert no influence on the other. The potential due to the smaller sphere at $60 \text{ m}$ from it in Volt is

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

Assertion: $A$ positive charge particle is placed in front of a spherical uncharged conductor. The number of lines of force terminating on the sphere will be more than those emerging from it.
Reason: The surface charge density at a point on the sphere nearest to the point charge will be negative and maximum in magnitude compared to other points on the sphere.

$A$ thin metallic spherical shell contains a charge $Q$ on it. $A$ point charge $+q$ is placed at the centre of the shell and another charge $q'$ is placed outside it as shown in the figure. All the three charges are positive. The force on the central charge due to the shell is:

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

The intensity of the electric field at a charged point inside a hollow metallic container is ....... .