FARADAY'S CAGE

INTRODUCTION

Most of us believe that Faraday's cage is a special enclosure, but, on the contrary it is quite a simple setup and can be easily made at home. All it requires is a conducting metallic cage and a zero potential point (which is not that essential).

PRINCIPLE

It is based on the principle of electrostatic shielding and the fact that electric field inside a pure conductor is zero. Let's see a diagram- 

Here we assume a BLUE conductor which has a cavity (shown in green). Now, we place two charges q1, and q2 (yellow inside cavity and pink outside the conductor).

Now, actually some charges get shifted in the conductor so that the net electric field inside the conductor is zero. 

By Gauss law we can safely say that these charges are not on the interior of the conductor but on the periphery of the conductor and the cavity inside it. The pattern of these charges are complex in nature.

If we move the charges q1 and q2, then the charges rearrange itself for only one thing- to make the conductor's electric field zero.

However, if we move only q1 (inside the cavity only), then the pattern of charges on the cavity's periphery changes but outer surface remains the same. Similarly, if we move q2 only, then the outer surface's charge pattern changes and the cavity charge pattern remains same. The reason is simple- to Validate the fundamental Gauss Law. That's why we call it a faraday cage- As the inner charge don't affect the outer charge conditions and vice-versa. Below diagram shows it-

(Source- Backyard brains)

This also means that any closed conductor can behave like a Faraday's cage. Mostly, we use a wire mesh of copper or aluminium but a hollow shell type was used by Faraday himself when he sat inside one! 

More for next time

Until then, BYE!