Gauss' Law and the Faraday Cage

[TheImpossibleDream]

This threads hurts mah thinken partz

[ExileStrife]

I don't want to argue what would happen in an ideal/perfect environment with perfect conductors with material permittivity = 0 and gaps in the cage approaching 0.  I can show this with an example.

Similarly, take a conducting wire, or a conducting plane and connect it between ANY two inner surfaces of the cage. There will be no current.

Any typical voltmeter would probably read zero in this case.  You can simplify this further and take an uninsulated wire and connect it to the two terminals of a battery.  If you take the leads of a voltmeter and touch them anywhere on the wire, you'll get a reading of zero.  But is that finite distance between the leads that's being measured for a change in potential truly some kind of mystery material that defies laws of thermodynamics?  Probably not.

Simple textbook theory usually does not account for energy loss due to the permittivity of conductors since it's SOOOO negligible.  However, you might find a practice problem or two that has you calculate the lag time or potential difference between a few miles of electrical cable used for power-lines or something, and you'll find that your answer is definitely not 0.  Of course, if that's true for a few miles of cable, it's also true for a couple of centemeters of wire.  If you take a VERY FINE voltmeter, you can measure this tiny potential difference.  And where there's potential differences, there are electric fields.  Yaaay, we found them!

Amplify the source and you'll get non-trivial currents out of it.    --As well as a lot of heat before that tiny wire decides to burn up.

[OrchardOfMines]

This has actually been tested:

http://www.youtube.com/watch?v=be6nLcUagL0

[ExileStrife]

Excellent.

[9lives]

Meta-trolling.

[Underbard]

Strife hit the nail on the head, and for any of you that are so smart you don't believe it, I have a different test for you.  Get out of the house for some fresh air.... Take a friend with you...Take a walk with said friend near a pasture... let said friend hold your arm while he urinates on an electric fence and notice how the current doesn't bother him... Also, notice how it does bother you.... Go back inside your house and stay out of the fresh air for a few years like you did before this test.

[DangerousDan]

Meta-trolling.

[ThatsMathematics]

Let's keep in mind that the example you gave just happens to be of a performer. I'm not personally familiar with his work, but I'm naturally skeptical about it (especially with a stage name like "Mindfreak"). But what about something closer to real life?

High Power Worker

By the way, I'm very surprised by the choice of stainless steel for the cage. Stainless steel is a horrible conductor of electricity and you'd expect it to heat up quite a bit. Nonetheless, it seems to manage the job just fine.

Of course, we could very well say that at a certain level, the electric field becomes so potent that the non-ideal nature of the conductor becomes evident and current would deviate from the outermost surface and begin moving closer to the inside. At this level however, we can be fairly sure that anything without the protection of a Faraday cage would have no chance of even surviving the experience.

As for a wire connecting the terminals of a battery, you are mistaken. Of course there would be very significant current, even from a torch battery. If it were a half-decent battery (low internal resistance), then of course you would measure a small voltage across two points of the wire.

I can understand why it is difficult to accept the Faraday Cage. It's not very intuitive. There is something that you must accept about intuition however; intuition is by and large a product of our evolutionary history. We are excellent at conceptualizing ideas that were relevant to our hominid ancestors, but that makes us very bad at understanding quantum effects, general relativity and electromagnetism.

Allow me to demonstrate. The shapes in our universe operate in 3 dimensions: left-right, back-forward, up-down. No doubt you can effortlessly conceptualize a three dimensional cube. Great. But now conceptualize a four dimensional "cube" (don't add time. That's cheating). As you begin to realize how limited our minds are, you begin to realize that science can't go around looking for intuitive solutions.

This is why we have mathematics and Maxwell's laws: so that we can just calculate the effects and not need to fully conceptualize the mechanism of electromagnetism (which are truly a complete explanation of the effects of electromagnetism).

If I told you that two events can occur at a different order in time depending on your frame of reference then the sane man would have every reason to be skeptical. If I told you that space is expanding into itself, you might laugh at me. If I said that electrons are both waves and particles, if you had no experience with quantum physics then you'd probably have a hard time swallowing that too.

The Shrodinger's cat mind experiment is an excellent example of the utter failure of humans to explain quantum physics in terms which they can relate to and understand.

So when I come in with an example of a physical effect which violates the water-flowing-through-slanted-pipes metaphor of the electrical circuit torted by high school teachers, of course it won't sit well with you. Far from the laws of thermodynamics, Ohm's law operates very well in its special domain but has issues as you leave that domain. Using Ohm's law to explain the Faraday cage is like trying to use a vacuum cleaner to extract wine stains from your carpet.

At the very least, I hope that you will accept the existence of the phenomenon. In fact, don't accept what I say. Find other sources. Electromagnetism is an interesting subject, and you don't need to blindly hang on to my every word. Needless to say though, I think that this back-and-forth discussion isn't getting us anywhere and you need to be convinced somewhere else.

[Egon the Monkey]

[ExileStrife]

High Power Worker

Did you watch that movie?  They say it right out in the open, "we are isolated from ground."  If they dropped a cable to the ground they'd be fucked, and they know it.  That guy's faux-faraday-suit would not be enough to save him from harm.

As for a wire connecting the terminals of a battery, you are mistaken. Of course there would be very significant current, even from a torch battery. If it were a half-decent battery (low internal resistance), then of course you would measure a small voltage across two points of the wire.

I'm not wrong about this.  Go try it.  From the way you're writing, I'm assuming you're still in acedemics and have easy access to a lab.  One small, unbroken, and uninsulated wire hooked up to a battery and touch the leads of a regular voltmeter anywhere on that wire it and you'll get ~0 V.  Of course there is current flowing through it, but that's not what you're measuring -- you are measuring a difference in potential or in this case, the lack thereof.  Perhaps there was just a misunderstanding...if you clipped that wire and put one lead on one part of the wire, and the other on the other, you'd see the potential difference at just about whatever the battery advertises.

You don't understand/trust mathematics

I do.  I don't know what qualifications I need to give you to make you believe that I do.  Back in college, I took two semesters of multivariable calculus, a physics based course in electromagnetism, an electrical engineering course in electrodynamics, and a fistful of lab work.  More importantly though, and what I believe is more relevant here, is one, I understand the difference between "real life" and "textbook theory," and two, I have actually done stuff inside of a faraday cage.  And guess what, despite the setup being very good, there was still measurable error we had to account for due to outside electromagnetic interferance.*

Even Maxwell's laws fall short in real life.  While they are the basis for describing a real-life system, you will NEVER, EVER actually measure something and have that measurement exactly equal whatever your equation predicts.  Everything has error.  Even superconductors have error.  Go do some advanced experiements or some labs so you can get some exposure to how significant error really is.  Since you seem to like "math," you'll probably love doing error propogation and confidence testing.

*It was actually a virtual lab where we were given an electromagnetic field combined with values of the cage to conduct the experiment inside of, and the point was to determine it's effects.  This was easier to do than actually using one of the cage labs because electromagnetic conditions are always changing in those. But it's the same thing regardless.

[ScottyB]

Cats aren't waves, they're meat.

[Sternhund]

Having taken courses in electromagnetism, I'm a tad more convinced by Strife's arguments. >_>

To address the suggestion itself: Neat idea, but adding electrical immunities to already awesome 8 AC Full Plate armors may disrupt the balance of the gameworld.

If Schroedinger's Cat walks into a forest, and no one is around to observe it, is he really in the forest?

Sternhund goes back to making molecules...

[ScottyB]

We'll know if a tree falls on it.

(BTW, Splat Cat.)

(If anyone gets that reference I love you.)

[Sternhund]

[lovethesuit]

I guess the real question is

If you put a faraday cage on a treadmill can it take off?