Statement:
"The electric field is zero everywhere inside the conductor, whether the conductor is solid or hollow."
Question:
A coaxial cable consists of a long, straight filament surrounded by a long, coaxial, cylindrical conducting shell. Assume charge $Q$ is on the filament, zero net charge is on the shell, and the electric field is $E_1\hat{i}$ at a particular point $P$ midway between the filament and the inner surface of the shell.
Next, you place the cable into a uniform external field $2E \hat{i}$. What is the $x$ component of the electric field at P then?
(a) 0
(b) between 0 and E1
(c) E1
(d) between 0 and 2E1
(e) 2E1
Answer:
Answer (c). The outer wall of the conducting shell will become polarized to cancel out the external field. The interior field is the same as before.
My Problem:
Wasn't it suppose to be 0 inside a conductor in whatever condition while it is in equilibrium? How come is it a non-zero value? I would expect the conducting shell to cancel out the electric field within it. That's what I've seen in the previous questions I've solved. Please explain.
