Question

an isolated conductor of any shape has a net charge of 10 microcoulomb inside the conductor is a cavity within which is a point charge of 3 microcoulomb what is the charge on the cavity wall? on the outer surface of the conductor.

Answer 1

$\bold{13 \times 10^{-6} \mathrm{C}}$ is the charge on outer surface.

Solution:

Here the Gaussian surface is within the conductor where at electrostatic equilibrium the electric field is zero.

Hence total electric flux shall become zero therefore as a result the enclosed net charge shall become zero

Net charge on conductor is $10 \times 10^{-6} \mathrm{C}$

Charge within the walls of cavity is $3 \times 10^{-6} \mathrm{C}$

Therefore charge on outer surface on conductor  

$=\left(10 \times 10^{-6}\right)+\left(3 \times 10^{-6}\right)$

Thus the value of charge on outer surface is $13 \times 10^{-6} \mathrm{C}$