Faraday Cage - Electroscope
To demonstrate that the electric field within a closed surface is zero.
Double wire strainer Faraday cage with electroscope, charging materials, and projection point source.
Charge the two wire strainers, which are connected electrically to the electroscope indicator. With the two meshes separated, the electroscope deflects. When they are placed together, forming a closed sphere, the electroscope deflection is zero, indicating zero potential within the closed cage. ◙