Question

Inside the three-dimensional conductor body is an inflatable cavity. What is the electric field in the cavity when the total charge of the conductor is + Q? And what can you say about the potential in the cavity?

Answer 1

For the closed conducting body, which enclosed Q charge, then total electric flux through the body,

$\phi = \frac{Q}{\epsilon_o}=EA$

Now, So electric field inside the cavity $E=\frac{kQ}{R^2} \frac{δ}{(δ^2−1)2}$

Potential inside the $V= E.dx$