Question

A thin metallic spherical shell contains a charge $Q$ on its surface. A point charge $q_1$ is placed at the centre of the shell and another charge $q_2$ is placed outside the shell. All the three charges are positive. Then, the force on charge $q_1$ is

• A. Towards right
• B. Towards left
• C. Zero
• D. None of these

Answer 1

The correct option is C Zero

Force on charge will depend on the electric field intensity at that place.
Considering a spherical Gaussian surface inside the shell.
Here $q_{enclosed}=0$ because $+q_1$ is a test charge and $+q_2$ and $+Q$ are outside the Gaussian surface.
$\therefore E=0$

Thus, the force experienced by charge $+q_1$ at centre of shell is zero.

Also since $q_1$ lies inside the conductor, it is always shielded from outside charges($q_2$) and electric field. This process is also known as electrostatic shielding.

So, $\left(c\right)$ is the correct choice.