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 fig. All  the three charges are positive. The force on the central charge due to the shell is :-

For the situation shown in the figure below, mark out the correct statement

Obtain the relation between electric field and electric potential.

‘The interior of a conductor can have no excess charge in the static situation’. Explain.

A conducting sphere of radius $10\, cm$ is charged $10\,\mu \,C$. Another uncharged sphere of radius $20\, cm$ is allowed to touch it for some time. After that if the sphere are separated, then surface density of charges, on the spheres will be in the ratio of

An empty thick conducting shell of inner radius $a$ and outer radius $b$ is shown in figure.If it is observed that the inner face of the shell carries a uniform charge density $-\sigma$ and the surface carries a uniform charge density $ '\sigma '$

If another point charge $q_B$ is also placed at a distance $c ( > b) $ the center of shell, then choose the correct statements