Faraday Cage:
A Faraday cage or Faraday shield is an enclosure made of a conducting material. The fields within a conductor cancel out with any external fields, so the electric field within the enclosure is zero. These Faraday cages act as big hollow conductors you can put things in to shield them from electrical fields. Any electrical shocks the cage receives, pass harmlessly around the outside of the cage.

An isolated point charge +q is placed inside the Faraday cage. Its surface must have charge equal to-

Options

A. Zero
B. `+q`
C. `-q`
D. `+2q`

Answer

C

Explanation

If a charge is placed inside an ungrounded Faraday Shield without touching the walls of the internal face of the shield becomes charged with -q and +q accumulates on the outer face of the shield. If the cage is grounded, the excess charges will be neutralized by the ground connection.