Jerry Foss, Chuck McCreary, Cecil Miller

shootceaselessUrban and Civil

Nov 16, 2013 (3 years and 6 months ago)

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Jerry Foss, Chuck McCreary, Cecil Miller

October 13, 2010

Faraday Cage Experiment


The Faraday cage, an effect discovered by Michael Faraday in 1836,
depends on these principles. A Faraday cage is an enclosed conducting
shell. It can be a solid conducting

shell or a shell made of wire mesh; the
important thing is that it completely encloses a region.

This hollow conducting shell will have no electric field inside, even when
placed in a very strong external electric field because the charges on the
conducti
ng surface rearrange themselves until the electric field inside is
zero. A Faraday cage also works in reverse. If there is a strong electric field
inside, the field outside the cage will be zero.

This Faraday cage effect causes Faraday cages to act as shie
lds for strong
electric fields or other electrical effects. In addition electromagnetic waves
consist of oscillating electric and magnetic fields. Therefore Faraday cages
effectively shield electromagnetic waves or electromagnetic radiation as
long as the
holes in the wire mesh are significantly smaller than the
wavelength of the electromagnetic waves. For this reason Faraday cages
are sometimes called Faraday shields.

Perhaps the most dramatic application of Faraday cages is
lightning safety
.

If lightning strikes a closed metal aircraft or car, the occupants are safe as
long as they are not in electrical contact with the outside metallic surface.
The encl
osed metallic car or aircraft acts as a Faraday cage and shields
the interior from the strong electric field of the lightning strike.

AC currents induce changing magnetic fields which in turn induce electric
fields. These electric fields can disrupt sensit
ive electronic devices, so they
use Faraday cages to shield crucial electronic components from stray
electromagnetic fields. Coaxial cables are surrounded by a conducting shell
to provide Faraday shields.

Faraday cages block electromagnetic waves. Building
s or rooms can be
deliberately built as Faraday cages either to prevent electromagnetic
interference for sensitive electronics or to prevent external spying in high
security situations. Buildings or rooms with significant amounts of metal in
their construc
tion might not be deliberate Faraday cages. They can
however act as such and block cell phone and other wireless
communication.

Our experiment consisted of testing four materials to see which one(s)
would be applicable to build a Faraday Cage. The tests co
nsisted of
Tensile Strength, Resistance, Flammability, and Voltage Capacity. Here
are the results:



Tensile

Strength

Resistance

in
Ohms

Flam
mability

Voltage Cap.

CUS

Poor

Increased 1/3
per ft (55
ohms/ft)

Fast

Fair

Ag

Fair

Doubled per
ft (13
ohms/ft)

Fair

Good

Poly Pyrrole

Good

Doubled per
ft (2K
ohms/ft)

Non
-
Flammable

Poor

Poly Pyrrole
.1mm

Poor

Doubled per
ft (71
ohms/ft)

Very Fast

Fair


Bases on the research data
,

the chart information indicates
that the copper
sulfide and poly pyrrole .1mm
were discarded due to the flammability of the
material or lack of the material to conduct electricity. The two remaining
materials,
poly pyrrole
and the silver material, could be used in a simple
weave pattern for maximum tensile strength and voltage capa
city.