A Faraday cage—a conductor surrounds a region. What is the electric field inside the interior when an external static field is applied?

A Faraday cage—a conductor surrounds a region. What is the electric field inside the interior when an external static field is applied?

• A. Interior field is zero.
• B. Interior field is nonzero and shielded.
• C. Interior field is nonzero and increases with distance.
• D. Interior field is undefined.

Answer: (A)

When a conductor is in electrostatic equilibrium, free charges rearrange themselves so that the electric field inside the conducting material is zero. In a Faraday cage, an external static field pushes charges to the outer surface and the induced charges create a field that cancels the external field inside the conductor. Because the metal is at one constant potential, no electric field lines penetrate the wall into the hollow interior. As long as there are no charges placed inside the cage, the interior region experiences zero electric field.

When a conductor is in electrostatic equilibrium, free charges rearrange themselves so that the electric field inside the conducting material is zero. In a Faraday cage, an external static field pushes charges to the outer surface and the induced charges create a field that cancels the external field inside the conductor. Because the metal is at one constant potential, no electric field lines penetrate the wall into the hollow interior. As long as there are no charges placed inside the cage, the interior region experiences zero electric field.