posted on May, 29 2012 @ 03:33 PM
First of all, where did this aluminum idea come from? Aluminum is diamagnetic (high resistance to a magnetic field) and therefore will not shunt the
electromagnetic pulse around whatever is inside. A Faraday Cage needs to be made of something which has ferromagnetic (low resistance to magnetic
fields) properties. Steel is OK, iron is pretty good, some of the shielding alloys (UltraPerm) are excellent.
A ground cable is not needed, unless you're worried about static buildup.
One of the best Faraday cages around is the trunk of a car. It's not perfect, primarily because the front is typically covered only by fabric, but it
does offer a good deal of protection. If one wanted to carry a Faraday cage with them, I would simply install a piece of sheet steel across the back
of the rear seat.
The problem with an EMP is that the high magnetic flux change that accompanies it will induce high voltages in any conductor it crosses. That means
that inside a piece of electronics, every wire, every trace on a circuit board, every component lead will become a small battery. The combination
tends to burn out the components, rendering the device useless even after the EMP has passed.
Certain components are more capable of withstanding EMPs. Coils and resistors are pretty hardy, as are switches and almost anything
electro-mechanical. Capacitors are so-so, as they are sensitive to high voltages beyond their rating, but they also can absorb spikes depending on
their value and the amount of energy in the voltage spike. Semiconductors are pretty susceptible in general, but those which use MOSFET technology
(most semiconductor chips, power transistors, etc.) will pop at the first sign of a spike in voltage. These last devices are so sensitive, special
care must be taken to put them together into a product; improper handling can cause them to blow without notice or even indication.
A Faraday cage works by channeling magnetic and electric fields around itself, keeping them from interfering with what is inside. Thus, the thicker
and less resistive the material is, the more current and flux it can channel around itself. The thinner and more resistive the material, the more it
will allow the fields in an EMP to travel through without diverting.