JEE MAIN - Physics (2019 - 12th April Morning Slot - No. 22)

Shown in the figure is a shell made of a conductor. It has inner radius a and outer radius b, and carries charge Q. At its centre is a dipole $$\overrightarrow P $$ as shown. In this case : JEE Main 2019 (Online) 12th April Morning Slot Physics - Electrostatics Question 167 English
surface charge density on the inner surface is uniform and equal to $${{\left( {Q/2} \right)} \over {4\pi {a^2}}}$$
surface charge density on the inner surface of the shell is zero everywhere
surface charge density on the outer surface depends on $$\left| {\overrightarrow P } \right|$$
electric field outside the shell is the same as that of a point charge at the centre of the shell

Explanation

Total charge of dipole = 0, so charge induced on outside surface = 0.

But due to non uniform electric field of dipole, the charge induced on inner surface is non zero and non uniform.

So, for any observer outside the shell, the resultant electric field is due to Q uniformly distributed on outer surface only and it is equal to.

$$E = {{KQ} \over {{r^2}}}$$

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