pulkit Posted August 8, 2004 Posted August 8, 2004 And use the best conductor you can get your hands on, of course For this application, why would small differences in conductivities (like those between different metals) matter ?
Kedas Posted August 8, 2004 Posted August 8, 2004 secondly' date=' WHAT WAVES????? we are talking about being hit by lightening, lightening is a discharge of static electricity from the clouds, it surely is a flow of electrons, which would not classify as a wave....... so what are you talking about?[/quote'] Good question A spike is a collection of many waves with a different wave lengths (wide spectrum) so it's a wave
pulkit Posted August 8, 2004 Posted August 8, 2004 Or think of current, then think of voltages, which are nothing but gradients of electric fields. The wave are of this electric field .(Which is precisely what they are made of in EM-radiation.)
5614 Posted August 8, 2004 Author Posted August 8, 2004 i was intending on putting on a metal suit and elctrocuting myself!!!! so your saying that an electrical current is actually a wave? that a lightening bolt, which i had always thought of as a flow of electrons is actually a wave? and when pulkit says: "The wave are of this electric field" what does that mean, i sorta get it, but "the wave are of...", its the "of" which is confusing, what does "The wave are of this electric field" mean? and how big are these waves, because were one to be making a electric proof metal mesh, you would need to know the wavelength, are we dealing with, X-ray 'size' rays, or radio 'size' waves?
pulkit Posted August 8, 2004 Posted August 8, 2004 Simple question : When you talk of any em radiation as a trasverse wave, what do you think is oscillating ? It is nothing but the electric and magnetic field, no particles are involved. This is what I meant by saying "wave of ..." . We quickly think of a sinousoid when the word wave is mention but often forget to think whose variation is the sinousoid referring to .
5614 Posted August 8, 2004 Author Posted August 8, 2004 thnx pulkit... Good question A spike is a collection of many waves with a different wave lengths (wide spectrum) so it's a wave spike????? whats a spike? i asked, is a lightening bolt a wave? [i thought it was a discharge of static electricity from the clouds, which would surely just be a flow of electrons? and how big are these waves, because were one to be making a electric proof metal mesh, you would need to know the wavelength, are we dealing with, X-ray 'size' rays, or radio 'size' waves?
5614 Posted August 9, 2004 Author Posted August 9, 2004 anyone?, any answers... [to my question, in my last post...]? please! thnx!
[Tycho?] Posted August 10, 2004 Posted August 10, 2004 anyone?' date=' any answers... [to my question, in my last post...']? please! thnx! Alright, if you dont know this stuff, it can seem confusing. Electricity can be a wave if its AC. AC means alternating current. Electricity is indeed a flow of electrons. But with AC, the direction they move in changes back and forth. Say at first they move from left to right, then it changes, going right to left. This can be expressed as a sinosodal wave, where one peak is electrons in one direction, the trough is electrons in opposite direction. It is expressed in the same units too. Say it changes direction, or alternates, 20 times a second. Its frequency would be 20hertz. Just like a wave of light is measured in hertz, or a wave of sound. Only AC current has a wave like this, direct current (DC) does not. (as far as I know, this may contain errors)
5614 Posted August 11, 2004 Author Posted August 11, 2004 no, [tycho?] that is correct, i knew all of that, i suppose i didnt think of an AC current as a wave of such, even though it moved back and forward, but the reason i didnt think of it as that was because a discharge of static electricity from the cloud, otherwise called lightening would be DC... if the clouds were positive, a load of electrons would flow to the sky, they sky would then become neutral, walla, all done, in one direction, therefore i assumed is would be DC, [and vice versa if the clouds were negatively charged] so the question i meant to ask was, how can a lightening bolt DC be a wave? thats what i didnt understand! and after all, this whole thread was originally [on pg1, about faraday's cage in relation to a lightening bolt!]
Kedas Posted August 11, 2004 Posted August 11, 2004 anyone?' date=' any answers... [to my question, in my last post...']? please! thnx! I found this link that should help you understand. http://www.boltlightningprotection.com/Elemental_Faraday_Cage.htm They mention a spectrum for lightning 1kHz to 1MHz. It's a good link you will probably find more info there that you are looking for. 'spike' (I mean a high value and short event) It is not really a wave(s) but Fourier explained that we could build up any signal form out of a lot of sin waves. And the big advantage is that we are very handy in the mathematical field if we have sin waves. So when you analyse all sin waves separately (mathematically) and then add all results together then you will have the same as trying to analyse that one not sin form wave and that is the big power behind it. Fourier: http://www.ling.mq.edu.au/units/slp801/acoustics/ch01s04.html
5614 Posted August 11, 2004 Author Posted August 11, 2004 damn, knew i knew what spike was, probably heard is in a lesson or something! im not very advanced at that kind of maths, whilst i understood what you said, please dont go into too much more detail, as you will probably loose me! and so what i understand from this website is that it is possible, to withstand an electric shock, providing, the faraday cage is of good enough quality, something which is more theoretical, and less practical BUT DOES WORK. so my next question is, [im endless question box in this thread!!!] is:- if you are sitting in a car, and it gets hit by lightening, are you safe, whilst the faraday effect does come into action, it is not necesarily all an electrical conductor due to glass and that it might not be totaly electromagnetically sealed around the door for instance other than that: am i correct in saying then, that a suit of aromour, all sealed? would theoretically protect you from lightening, however as the metal may not be of high enough conductivity rate, it might not practically work, but theoretically it will!
5614 Posted August 15, 2004 Author Posted August 15, 2004 if you put a metal bucket over your head, and the bucket got hit by lightning, would you be safe. i dont think so, as the bucket would not be sealed at the bottom, another question, if your car got hit by lightning, would you be safe, as it does act as faraday's cage, except that the windows [glass] are not conductors, so i dont know, however they are sealed?
swansont Posted August 16, 2004 Posted August 16, 2004 another question, if your car got hit by lightning, would you be safe, as it does act as faraday's cage, except that the windows [glass'] are not conductors, so i dont know, however they are sealed? The size of the holes tells you what frequencies are shielded by the cage. Lightning is basically a DC signal, so you can have big holes - it becomes a circuit problem; what path gives low resistance to the current. If you expected your car to protect you from radio waves or higher frequencies, then you'd have to worry about holes. The idea here is similar to why radio telescopes can be made of mesh/honeycomb but visible telescope reflector "dishes" are mirrors.
Wolfman Posted August 16, 2004 Posted August 16, 2004 I know someone who was in a car when it got hit by lightning here in FL and nothing happened to them so there is your answer. It could have something to do with the fact that the tires are rubber wich is not a conductor.
Lance Posted August 16, 2004 Posted August 16, 2004 I know someone who was in a car when it got hit by lightning here in FL and nothing happened to them so there is your answer. It could have something to do with the fact that the tires are rubber wich is not a conductor. A few feet of rubber doesn't add much resistance considering the resistance of the air above the car.
5614 Posted August 16, 2004 Author Posted August 16, 2004 A few feet of rubber doesn't add much resistance considering the resistance of the air above the car. i read that, and thought, yeah, good point, but then i remember a sad story, of two people, newly married, lived in the area, it was in the local paper. they'd gone on holiday, it was all sunny, and suddenly, randomly, they were hit by lightning, from no-where! i dont know where, it was sunny, maybe there were clouds as well, i wasnt there. so they were hit by lightning, one of them had thin sandles on, he survived, although he was nocked out cold for a bit, the other person died. apparently, his sandles had saved him, and they must have only been 1cm thick, so, who knows... tires, probably do help a bit, but to what extent, who knows!
Kedas Posted August 16, 2004 Posted August 16, 2004 It's about creatng an easier way around you so you won't be hit. about metal bucket etc. keep in mind that there should be a nice clear space between you and the Faraday cage otherwise you will part of the cage. a bad part
5614 Posted August 16, 2004 Author Posted August 16, 2004 If you were wearing a metal suit' date=' the current would stil be conducted through your body resulting in bad things. If you were in a faraday's cage, lets assume it's a big box (or a room as the boffins call it), you would not notice anything happening. The suit idea would protect you from EMP, but that isn't very useful if you still fry. If the suit was an oversized model, it could work.[/quote'] God damn it ! if u r inside a conducting shell u can't get a shock !!Don't you know anything about physics ??????!!!! Current needs a potential difference which you can't have in a conductor because it is equipotential. In short' date=' YOU CANNOT GET AN ELECTRIC SHOCK inside a faraday cage !! Completing a circuit is not enuf, you must have a driving potential.[/quote'] It's about creatng an easier way around you so you won't be hit.about metal bucket etc. keep in mind that there should be a nice clear space between you and the Faraday cage otherwise you will part of the cage. a bad part im confused, read the above quotes, all from this thread, and answer these simple question, but please, only answer if you are certain 1) if i wear a sealed metalic suit, of good conducting metal, and its touching my entire body, and it is hit by lightning, am i electrocuted? 2) if i wear a sealed metalic suit, of good conducting metal, and am NOT touching it at any point, and it is hit by lightning, am i electrocuted? 3) in other words, can i touch the faraday cage, and it still work? 4) if at all, at how many points can i touch the faraday cage? i.e. is one point fine, but two points complete a circuit, or what?
Wolfman Posted August 16, 2004 Posted August 16, 2004 please believe me when I say I knew someone who was in a car and lightning struck the top of it and that person wasnt even hurt. But then again a car isnt just made out of only metal, your practicaly not touching metal. you dont sit in a metal seat you dont touch a metal steering wheel and your shoes are more than likely not metal but rubber and again with the rubber tires. Maybe somebody can totally disprove what I just said but all I know is that person didnt even get hurt.
5614 Posted August 16, 2004 Author Posted August 16, 2004 i wouldnt have expected them to, they are insulated from the metal outter shell of the car, so this is not necesarily about faraday cage, i do believe you though! [promise]
[Tycho?] Posted August 16, 2004 Posted August 16, 2004 im confused' date=' read the above quotes, all from this thread, and answer these simple question, but please, only answer if you are certain 1) if i wear a sealed metalic suit, of good conducting metal, and its touching my entire body, and it is hit by lightning, am i electrocuted? 2) if i wear a sealed metalic suit, of good conducting metal, and am NOT touching it at any point, and it is hit by lightning, am i electrocuted? 3) in other words, can i touch the faraday cage, and it still work? 4) if at all, at how many points can i touch the faraday cage? i.e. is one point fine, but two points complete a circuit, or what?[/quote'] 1) Not really sure on this. If the metal is the path of least resistance (it should be) then electricity will flow through that... lightning has a ton of current though, so perhaps that must be taken into account. This should be answered by someone else. 2) Definately not. Lightning flows through metal, you arn't touching it, no harm whatsoever. edit: oh yeah and the car thing. A car is one of the safest places to be during a lightning storm, you will not be harmed even if the car is struck. It is commonly thought this is because of rubber tires, which are insulaters. I saw an experiment on tv once, where a big tesla coil was allowed to discharge next to a car. It was found that the lightning flowed over the car (skin effect I think) and that the protective effects was not due to the rubber tires.
5614 Posted August 17, 2004 Author Posted August 17, 2004 '']1) Not really sure on this. If the metal is the path of least resistance (it should be) then electricity will flow through that... lightning has a ton of current though, so perhaps that must be taken into account. This should be answered by someone else. no, it wouldnt effect you, due to the fact that it is impossible to create a potential difference. '']2) Definately not. Lightning flows through metal, you arn't touching it, no harm whatsoever. correct '']edit: oh yeah and the car thing. A car is one of the safest places to be during a lightning storm, you will not be harmed even if the car is struck. It is commonly thought this is because of rubber tires, which are insulaters. I saw an experiment on tv once, where a big tesla coil was allowed to discharge next to a car. It was found that the lightning flowed over the car (skin effect I think) and that the protective effects was not due to the rubber tires. this is not the skin effect, this is a faraday cage. i have to say, faraday cage is quite cool! question: if there was a whole, bigger than the wavelength of the wave, does that immediately cancel all effect of the faraday cage? i would assume so... additionally what is the 'wavelength' of a dc signal, in this case, the lightning?
swansont Posted August 17, 2004 Posted August 17, 2004 question: if there was a whole' date=' bigger than the wavelength of the wave, does that immediately cancel all effect of the faraday cage? i would assume so... additionally what is the 'wavelength' of a dc signal, in this case, the lightning?[/quote'] Basically, yes. It's not a sharp cutoff, though. A DC signal has an infinite wavelength and zero frequency.
5614 Posted August 17, 2004 Author Posted August 17, 2004 A DC signal has an infinite wavelength and zero frequency. in which case, what size holes are we talking about, which would make the faraday cage effectively useless?
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