Faraday cage

Many people must have experienced the embarrassment of their mobile phone ringing in the least appropriate moment. It can't easily be prevented unless you are in the possession of so called Faraday cage.

Faraday cage is a kind of enclosure with is a screen made of metal gauze. It is used to shield the inside of the enclosure from the outside electric fields. The strength of the electric field inside the Faraday cage is zero. A sieve covered with aluminium foil could be such a cage.

All this can be proved. Place an electroscope inside the cage. The one from the next experiment could be used. Even if we strongly electrify the cage using, for example, the piezo-electric switch or the electrostatic generator (we can do it by connecting another electroscope to the outer surface of the wire gauze), the lobes of the inside electroscope will not move.

Similarly, the mobile phone placed inside the cage doesn't work.