Question: Hi Colin, I have a big interest in Physics and I was wondering how a Faraday Cage works. I'm fascinated by how if you stand in one, you cannot receive an electric shock. I'm asking you because I believe this is a Physics styled question. Thanks!

Colin Johnston answered on 11 Nov 2014:

A Faraday cage is basically a hollow metal box or cage. Metals are conductors of electricity with freely moving electrons in them.
If an external object with a positive electrical charge approaches the cage, the negatively-charged electrons are drawn to that external object. Electrons with the same charge towards the external object are repelled and move away from the object. Or if the external object has a negative charge the electrons are repelled by it. This movement of charges is called electrostatic induction.
With the external charged object present, one side of the cage ends up with a negative charge and the opposite side with a positive charge. The result is an opposing electric field that cancels out the field of the external object’s charge inside the cage. The net electric charge inside the cage is zero.
The opposing electric field does have the important effect of shielding the inside of the cage from exterior static electric charges and also from electromagnetic radiation, like radio waves and microwaves, if the conductor is thick enough and any holes are significantly smaller than the radiation’s wavelength.
Faraday cages are very important in testing electronic devices as they block radio, wifi and cell phone signals from interfering with the device under test.

I hope this helps you.