Solved: Faraday Cage Problem - No Electric Charge on Man

Click For Summary

Discussion Overview

The discussion revolves around the effects of lightning on a man standing on a rubber mat inside a Faraday cage. Participants explore various scenarios regarding whether the cage, the man, or both would be charged when lightning strikes, considering the implications of the rubber mat's insulation and the nature of electric charge distribution.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that both the cage and the man would be charged if the man is touching the cage, as there is no path for the electricity to escape, assuming the rubber mat remains effective.
  • Others argue that if the cage is on the rubber mat, it may not be charged at all, suggesting that the rubber insulation prevents any charge from reaching the cage.
  • A participant raises a concern about the implications of a woman touching the man inside the cage, questioning whether she would be harmed due to the charge transfer.
  • Some participants discuss the scenario where the cage is grounded instead of on the rubber mat, suggesting that in this case, the man would not be harmed as the charge would go to the ground through the cage.
  • One participant mentions that the charge in the man would rise and fall with the cage's potential, indicating a shared charge between the man and the cage, but the safety of the man remains uncertain.
  • Another participant introduces a comparison to power lines and cars, explaining that cars act as Faraday cages and that touching a charged surface can still result in harm.
  • Some participants reference external sources to argue that the person inside a cage can remain uncharged, leading to differing interpretations of the situation.
  • There is a discussion about the differences between lightning and Tesla coil effects, with one participant emphasizing that real lightning behaves differently and can penetrate the body, unlike high-frequency Tesla effects.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the man, the cage, or both would be charged during a lightning strike. Multiple competing views remain, with some asserting that nothing will be charged, while others believe that both the man and the cage will share the charge.

Contextual Notes

The discussion highlights various assumptions regarding the effectiveness of the rubber mat, the grounding of the cage, and the nature of electric charge transfer during lightning strikes. Participants reference different scenarios and external sources, which may introduce additional complexities to the problem.

katchum
Messages
116
Reaction score
0
[SOLVED] Faraday cage problem

A man is standing on a rubber mat which is isolated. You place a Faraday Cage around the mat. (the cage is standing on top of the mat) The man is touching the cage

Now when lightning hits will:

1) the cage be loaded with electricity
2) the cage not be loaded with electricity
3) the cage and the man be loaded with electricity
4) the man only be loaded with electricity
 
Last edited:
Physics news on Phys.org
Opinion? I think the cage and the man would be charged; there's nowhere for the electricity to go (assuming it doesn't bleed through the rubber mat). If he man was not touching the cage, it would just be the cage that is charged.
 
I thought it too, note that the cage is also standing on the rubber mat. If now a woman would touch the man inside the cage, would this woman be dead because of the charge going through the woman?

Also, your shoes are of rubber too, so why would the electricity go through your body to the ground?

Now what happens when the cage is standing on the ground instead of on the rubber mat? The man is still touching the cage. I would think, nothing happens to the man and all the electricity will go through the cage to the ground.

edit: someone else says that the lightning can't possibly get to the cage when both man and cage are on the rubber mat. So nothing happens, no charge or anything like that...
 
Last edited:
katchum said:
A man is standing on a rubber mat which is isolated. You place a Faraday Cage around the mat. The man is touching the cage

Now when lightning hits will:

1) the cage be loaded with electricity
2) the cage not be loaded with electricity
3) the cage and the man be loaded with electricity
4) the man only be loaded with electricity

IF the man is touching the cage at one point, the charge in the man will rise as the charge in the cage rises in potential and fall as the cage falls. In short the man will be loaded with charge, and then unloaded as the charge goes to ground. If he touches the cage in two places then he will still charge with the cage but depending on where he is touching with respect to the strike he may become a conduit for the electricity as it flows to charge all parts of the cage equally.

Short answer? He and the cage share the charge. Whether he is also toast or not is another matter.
 
Anyone else? Because I believe nothing will get charged, answer 2)
 
wysard said:
IF the man is touching the cage at one point, the charge in the man will rise as the charge in the cage rises in potential and fall as the cage falls. In short the man will be loaded with charge, and then unloaded as the charge goes to ground. If he touches the cage in two places then he will still charge with the cage but depending on where he is touching with respect to the strike he may become a conduit for the electricity as it flows to charge all parts of the cage equally.

A similar thing is when power lines fall on cars.

http://beaufortusa.com/lightning_safety.htm
If caught in a car, stay inside. Although scary, you will be safer inside than outside. Even if power lines fall on the car, stay inside! Help will come. Sit in the middle of the seat away from the doors.
The car is insulted from the ground (rubber tires), but it also acts like a faraday cage (assuming you have an American car :biggrin:). The reason for sitting away from the doors is because the car's metal exterior is charged, and touching the doors can still run a charge through you. Faraday cage or not, touching something that is charged will charge you, and if you are touching two things that have different charges, you will get fried.
 
Last edited by a moderator:
Absolutely right Shawn.

Ususally the point of a Faraday cage is NOT to touch the charged body. IE: the man's sole contact with the cage is through the rubber mat then the charge goes into the cage, around him and to ground. High tension linesmen's suits actually have a fine layer of copper grid in between layers of the fabric so that when properly outfitted and grounded the linesman is shielded from the massive EM coming of the power lines.
 
Ah, so you are saying answer 3? I concur.

Okay, that is noted and therefore the problem is solved.
 
I'm afraid it's still not solved after I saw this:

http://www.mos.org/sln/toe/cage.html

The person in the cage can just touch the inside of the car without being 'charged'? Can you explain this?

So now I would say only the cage will be charged with alternating current and the inside is free of electricity. Answer 1!
 
Last edited:
  • #10
They are not talking about lightening.

They are using a Tesla setup to create their "Lightening". The difference is that lightning is very low frequency. Tesla bolts are very high freqeuency. The "skin" effect they metion refers to the fact that the higher the frequency of the signal the less the penetration depth into a body. So a real lightning bolt will go right through you, but a tesla bolt with frequenices up in the Ghz range actually travel on the outside of your skin. You could hold a florescent light bulb and get tagged with one of those bolts and all that would happen is your hair would stand on end and the light would glow. You are STILL charged if you interact with the electicity source. As I said before, whether or not you are toast or not is a different kettle of fish.

Nothing changed. They have just engineered a way for you not to get killed touching their "lightening". If you were insulated in a car and touched the charged body the reaction would be quite violent. Trust me. I have been clipped by lightening. The physical effects of messing with the power in one of mother natures lightning bolts is profound, immediate, and not at all subtle...lol
 

Similar threads

Graduate How Does Grounding Affect Safety Inside a Faraday Cage with a Tesla Coil?
  • · Replies 13 ·
Replies
13
Views
6K
Graduate Electric Field Shielding: Does a Conductor Shield Inside?
  • · Replies 4 ·
Replies
4
Views
4K
Undergrad Tesla Coil Surprises Inside a Faraday Cage
  • · Replies 5 ·
Replies
5
Views
4K
Graduate Levitation using directed electric fields
  • · Replies 13 ·
Replies
13
Views
6K
High School Solve FTL Problem with Faraday Cage and Relativity Theory
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Faraday Cage Concept and Building Questions
  • · Replies 1 ·
Replies
1
Views
10K
Graduate Can a lattice of insulating spheres create a faraday cage?
  • · Replies 14 ·
Replies
14
Views
3K
Graduate Faraday cage problem with RFiD
  • · Replies 12 ·
Replies
12
Views
10K
Graduate Effect of electric field on a wire segment
  • · Replies 4 ·
Replies
4
Views
2K
Building a Faraday Cage: Is 2-Layer Aluminum Screen Enough?
  • · Replies 6 ·
Replies
6
Views
5K