teexmmo@ioe.lon.ac.uk (Matthew Moore) (07/18/90)
>> [other stuff about a corona discharge (St. Elmo's Fire)] >> >>Maybe one could argue that by bleeding off the charge like that, one is >>less likely to take a hit (reducing the potential difference); but on the > ^^^^^^^^^^^^^^^^^^^^^^^^^ >This part is probably true. > >>other hand, pointy vertical rods are a much better target than other > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >>things (lightning rods, while generally saving a structure, do tend to >>increase its liklihood of being hit), and the fact that there was all this > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ >I know this is the commonly accepted idea behind lightning rods, but as I >learned in my college physics class, lightning rods actually REPEL lightning, >rather than ATTRACTING it. The physics behind it goes something like this: > The lightning rod MUST be grounded (electrically connected to the earth), > otherwise it's useless. The other important feature of a lightning rod is > that it is very pointy, not merely the highest point on a structure. > A few basic facts need to be introduced before getting to the actual > explanation. > - Lightning is a discharge of excess negative (-) charge toward a source > of excess positive (+) charge. > - Unlike charges (+ & -) attract; like charges (- & - , or + & +) repel. > - The earth is a natural source of negative charge. > Okay, with those things in mind, the lightning rod is therefore (by being > connected to ground) a source of negative charge. Due to the shape of the > tip of the lightning rod being pointy (more precisely, a VERY small radius > curve), the excess negative charge is radiated out from the tip of the rod > in all directions. (an explanation of that gets rather technical) > Therefore, with this field of negative charge radiating > out from the rod, a bolt of lightning (also negative charge) is REPELLED > from the rod, NOT attracted. > Lightning conductors _tend_ to prevent lightning strikes. A LC is an earthed rod, attached to the top of the protected structure. The base of any nearby thundercloud will be negatively charged wrt the earth. This charge induces a positive charge at the top of the rod (ie like charges repel, so the free electrons at the top of the rod are repelled down it, leaving net +ve charge at the top). Charge may be distributed irregurlarly on the surface of any charged conductor. In particular, it builds up and extends much further away from any pointed area. (This is known as point action). So the air above the pointy bits carries a high net +ve charge, and may become ionized, (causing the discharge seen). This ionized region is described as a space charge, and is what _prevents_ lightning discharge between ground and cloud. The mechanism seems to be similar to capacitance, in that potential between the two plates of a capacitor is reduced because one plate is earthed. Similarly, earthing the LC allows the flow of charge between earth and the pointy tips, causing a reduction in potential difference between cloud and ground. Cross-posted to physics and electronics, corrections very welcome via posting or email, particularly on the inferred similarity with capacitance. The convention wrt to current flow has been ignored as confusing, and the mechanism of lightning strike (leader spark from earth to cloud, followed by return discharge from cloud to ground) omitted for brevity.
kgreer@mcnc.org (Ken Greer) (07/20/90)
In article <1990Jul18.111525.5749@ioe.lon.ac.uk> teexmmo@ioe.lon.ac.uk (Matthew Moore) writes:
+++ [other stuff about a corona discharge (St. Elmo's Fire)]
+++
++I know this is the commonly accepted idea behind lightning rods, but as I
++learned in my college physics class, lightning rods actually REPEL lightning,
++rather than ATTRACTING it. The physics behind it goes something like this:
---------- stuff deleted -----------
+Lightning conductors _tend_ to prevent lightning strikes.
Ok, so "knowing" all this, as I understand it to be said, one should be
safer standing on the roof next to a lightning rod, instead of somewhere
else? Or do I completely miss the point?
--
Kim L. Greer try: klg@orion.mc.duke.edu
Duke University Medical Center kgreer@mcnc.org
Div. Nuclear Medicine POB 3949 klg@dukeac.ac.duke.edu
Durham, NC 27710 919-660-2711x5223 fax: 919-681-5636sjohnson@gumbee.mlb.semi.harris.com (Scott Johnson) (07/20/90)
In article <2436@speedy.mcnc.org> kgreer@mcnc.org.UUCP (Ken Greer) writes: >In article <1990Jul18.111525.5749@ioe.lon.ac.uk> teexmmo@ioe.lon.ac.uk (Matthew Moore) writes: >+++ [other stuff about a corona discharge (St. Elmo's Fire)] >+++ >++I know this is the commonly accepted idea behind lightning rods, but as I >++learned in my college physics class, lightning rods actually REPEL lightning, >---------- stuff deleted ----------- >+Lightning conductors _tend_ to prevent lightning strikes. more stuff deleted, I think... >Charge may be distributed irregurlarly on the surface of any charged >conductor. In particular, it builds up and extends much further away >from any pointed area. (This is known as point action). So the air >above the pointy bits carries a high net +ve charge, and may become >ionized, (causing the discharge seen). This ionized region is >described as a space charge, and is what _prevents_ lightning >discharge between ground and cloud. OK, The point will have a higher electric field and IF great enough it could cause ionization of the air in the vicinity. Ionization of gas creates a plasma (which will also be POSITIVELY charged, like the rod, since the electrons lost by the nitrogen molecules will be drained off by the conductor around which the field is concentrated) If the field is only strong enough to ionize the air in the immediate area, we have a cloud of glowing plasma around the conductor, (St. Elmo's fire I would assume); if we have a strong enough field to break down the air between the negative charge source in the atmosphere and the rod, then plasma is created along the entire length and a lightning strike results. If you see a traveling bolt of lightning, then you are seeing a ionization process begining first at the area of highest electric field. In this discussion we are talking about charges and fields of VERY LARGE proportions (look at the breakdown field for nitrogen) and I would not believe that the leakage current in air could ever have an effect on the eventual result (strike vs. no strike vs. other place struck). Also, resistance of almost any object (lets leave out rubber, plastic and such insulators, of course) is small when compared with the air, so whether we had an excellent ground or a 10K ohm ground i think is also irrelevent to the final result. With all this handwaving, I think we all should hire out as scarecrows! :) Kim Greer writes: > Ok, so "knowing" all this, as I understand it to be said, one should be >safer standing on the roof next to a lightning rod, instead of somewhere >else? Or do I completely miss the point? >-- Kim, I think they would tell you that this is a bad idea,unless you have a well conductive pointy head (which I've yet to see at Duke) in which case the lightning will avoid you also and strike a tree down the road. I, however, have heard enough of this nonsense! I didn't study E-mag and solid state physics this long to still be able to swallow these lines! (by the way there is also a car down at the Ford place that 3 people committed suicide in. They can't sell it and its going cheap...) I think maybe this 'lightning rods repel lightning' stuff was started as a cruel textbook joke to baffle physics students by some screwed up prof. CAN ANYONE COME UP WITH A REFERENCE? SURELY IF THIS 'STRANGE BUT TRUE STORY' IS FACT, THEN IT'S DOCUMENTED. i'D LIKE TO GET TO THE 'THEORY' BEHIND WHAT I CONSIDER VICIOUS RUMOURS ABOUT MY FAVORITE 'FIELDS'. :) The earth is round. Rock n Roll is best loud. Sailing is expensive, and lightning STRIKES lightning rods! Thats how they protect a house, they deflect the current! Come on guys! scott johnson: sjohnson@gumbee.mlb.semi.harris.com Melbourne, Fl sjohnson@booboo.mcnc.org Dept. of Electrical Engineering North Carolina State University Raleigh, NC
richard@locus.com (Richard M. Mathews) (07/20/90)
The following description of lightning and lightning rods is not correct. The main error is the claim that "the earth is a natural source of negative charge." This means the end result about lightning rods repelling lightning is also wrong. >>I know this is the commonly accepted idea behind lightning rods, but as I >>learned in my college physics class, lightning rods actually REPEL lightning, >>rather than ATTRACTING it. The physics behind it goes something like this: >> The lightning rod MUST be grounded (electrically connected to the earth), >> otherwise it's useless. The other important feature of a lightning rod is >> that it is very pointy, not merely the highest point on a structure. >> A few basic facts need to be introduced before getting to the actual >> explanation. >> - Lightning is a discharge of excess negative (-) charge toward a source >> of excess positive (+) charge. >> - Unlike charges (+ & -) attract; like charges (- & - , or + & +) repel. >> - The earth is a natural source of negative charge. >> Okay, with those things in mind, the lightning rod is therefore (by being >> connected to ground) a source of negative charge. Due to the shape of the >> tip of the lightning rod being pointy (more precisely, a VERY small radius >> curve), the excess negative charge is radiated out from the tip of the rod >> in all directions. (an explanation of that gets rather technical) >> Therefore, with this field of negative charge radiating >> out from the rod, a bolt of lightning (also negative charge) is REPELLED >> from the rod, NOT attracted. Here's the real scoop (source: The Feynman Lectures on Physics, Vol 2, chapter 9). Away from thunderclouds, the earth has a negative charge relative to "the sky." The potential difference is quite incredible: about 100 volts per meter. Why does this not electrocute you? Because your skin is so much better at conducting than air, your skin can be treated as a perfect conductor. Your head and your feet have the same potential as the earth. A foot from your nose, the air is at a potential of +200V. The "battery" which keeps this enormous potential charged is all of the thunderclouds in the world. Relative to the earth, most of the bottom of a thunderhead has a negative charge (the top of the cloud and a section in the middle of the bottom have positive charges). Over most of the world it is fair to say that "the earth is a natural source of negative charge." Near the cloud, however, the earth is positive relative to the cloud. Lightning is a discharge of the supercharged negative portion of the cloud to the positive ground. A sharp lightning rod will concentrate the positive charge of the earth and bring it up closer to the source of negative charge. The lightning rods do attract lightning. A lightning strike begins with a dark leader which moves in steps towards the ground. This leaves a trail of ionized, negatively charged air which conducts well. When the leader gets close to a sharp grounded point (perhaps a hundred meters), the electric field near that point gets very large. The air ionizes there, and a trail of positive charge moves up to meet the lightning leader (well, negative charges progressively farther and farther from the lightning rod move down into the rod). When the trail coming up from the rod and the longer trail coming down from the cloud connect, the circuit is completed and the bright stroke of lightning moves up to the cloud. The current is about 10000 amps at its peak, and it carries down about 20 coulombs of negative charge. All of the negative charge from all of the lightning strikes across the world spreads out across the planet and produce the 100 volts per meter potential difference observed under clear skies. Since some regions of the world have frequent morning thunderstorms and other regions have evening thunderstorms, the potential varies through the day. On the average it stays around 90 V/m from 0h to 12h GMT with a minimum at 4h GMT. It rises steadily to about 120 V/m at around 19h GMT and then drops steadily back to 90 V/m at 0h GMT the next day. Note that the potential varies over the whole world at the same time -- the peak is at a specific Greenwich time, not local time. Richard M. Mathews Locus Computing Corporation richard@locus.com lcc!richard@ucla-se.ucla.edu
kgreer@mcnc.org (Ken Greer) (07/21/90)
In article <1990Jul19.210925.165@mlb.semi.harris.com> sjohnson@gumbee.mlb.semi.harris.com (Scott Johnson) writes: >In article <2436@speedy.mcnc.org> kgreer@mcnc.org.UUCP (Ken Greer) writes: >>In article <1990Jul18.111525.5749@ioe.lon.ac.uk> teexmmo@ioe.lon.ac.uk (Matthew Moore) writes: >>+++ [other stuff about a corona discharge (St. Elmo's Fire)] >>+++ >>++I know this is the commonly accepted idea behind lightning rods, but as I >>++learned in my college physics class, lightning rods actually REPEL lightning, >>---------- stuff deleted ----------- > >> Ok, so "knowing" all this, as I understand it to be said, one should be >>safer standing on the roof next to a lightning rod, instead of somewhere >>else? Or do I completely miss the point? >>-- > >Kim, I think they would tell you that this is a bad idea [....] My (not quite sarcastic enough) point also. (See question below). > The earth is round. > Rock n Roll is best loud. > Sailing is expensive, > and lightning STRIKES lightning rods! > Thats how they protect a house, they deflect the current! > Come on guys! Agreed - (except for the part about R&R). My only question now to those who *seem* to be saying it deflects lightning (assuming "deflecting" means away from the lightning rod): Would you hold an umbrella (which is a lightning rod connected to ground by the person holding it) up during a lightning storm? I think not. I seem to remember some time back hearing (radio/tv?) that "protection" by lighting rods was just a hoax to con people into buying them - sort of like a vigilant pet rock - in years past. "Well, you mean you had lightning hit your barn and you *had* lightning rods??? Well, you must not have had enough of them up there". Yeah, right. I wish I had a reference for this. -- Kim L. Greer try: klg@orion.mc.duke.edu Duke University Medical Center kgreer@mcnc.org Div. Nuclear Medicine POB 3949 klg@dukeac.ac.duke.edu Durham, NC 27710 919-660-2711x5223 fax: 919-681-5636
davet@tsdiag.ccur.com (Dave Tiller N2KAU) (07/21/90)
In article <1990Jul19.210925.165@mlb.semi.harris.com> sjohnson@gumbee.mlb.semi.harris.com (Scott Johnson) writes:
-
-
-I, however, have heard enough of this nonsense! I didn't study E-mag and
-solid state physics this long to still be able to swallow these lines!
-
-I think maybe this 'lightning rods repel lightning' stuff was started as
-a cruel textbook joke to baffle physics students by some screwed up prof.
-
-CAN ANYONE COME UP WITH A REFERENCE?
-SURELY IF THIS 'STRANGE BUT TRUE STORY' IS FACT, THEN IT'S DOCUMENTED.
-i'D LIKE TO GET TO THE 'THEORY' BEHIND WHAT I CONSIDER VICIOUS
-RUMOURS ABOUT MY FAVORITE 'FIELDS'. :)
Popular Mechanics had an article on lightning protection for mountaintop
antenna installations. It used giant mushroom shaped wire mesh structures
to avoid the point charge buildup so the lightning would hit the mushroom,
_not_ be deflected toward the antenna tower. Unfortunately I can't provide
the chapter and verse, since it's been a few years, and my Pop Mechs are in
Va. Anyone else read this article?
--
David E. Tiller davet@tsdiag.ccur.com | Concurrent Computer Corp.
FAX: 201-870-5952 Ph: (201) 870-4119 (w) | 2 Crescent Place, M/S 117
UUCP: ucbvax!rutgers!petsd!tsdiag!davet | Oceanport NJ, 07757
ICBM: 40 16' 52" N 73 59' 00" W | N2KAU @ NN2Zbwhite@oucsace.cs.OHIOU.EDU (Bill White) (07/22/90)
In article <2438@speedy.mcnc.org> kgreer@mcnc.org.UUCP (Ken Greer) writes: >In article <1990Jul19.210925.165@mlb.semi.harris.com> sjohnson@gumbee.mlb.semi.harris.com (Scott Johnson) writes: >>In article <2436@speedy.mcnc.org> kgreer@mcnc.org.UUCP (Ken Greer) writes: >>>In article <1990Jul18.111525.5749@ioe.lon.ac.uk> teexmmo@ioe.lon.ac.uk (Matthew Moore) writes: >>>++I know this is the commonly accepted idea behind lightning rods, but as I >>>++learned in my college physics class, lightning rods actually REPEL lightning, >>> Ok, so "knowing" all this, as I understand it to be said, one should be >>>safer standing on the roof next to a lightning rod, instead of somewhere >>>else? Or do I completely miss the point? >>Kim, I think they would tell you that this is a bad idea [....] > My (not quite sarcastic enough) point also. (See question below). > >> and lightning STRIKES lightning rods! >> Thats how they protect a house, they deflect the current! >> Come on guys! > > My only question now to those who *seem* to be saying it deflects >lightning (assuming "deflecting" means away from the lightning rod): > > Would you hold an umbrella (which is a lightning rod connected to > ground by the person holding it) up during a lightning storm? I > think not. Well, I remember an article in some electronics magazine about this subject. It seems that yes, lightning rods can repel lightning, and yes, lightning rods can also attract lightning. It all depends on how well the thing is grounded! The big problem is, many lightning rods are not really well grounded, and as such, what they really do is just pick up the charge that's in the surrounding environment (read: the air). The article then stated that one of the best methods for lightning protection was to erect a grid of metal pipes above a structure, and leave it ungrounded. It seems that the lightning would then avoid the structure completely, as a like charge would be induced in the grid as the first (invisible) stroke occurred. On the other hand, a well-grounded rod (for a really good ground, you should have a bunch of "roots" coming off the ground rod in a star pattern, and salt the whole thing with copper sulfate or equivalent) will tend to attract lightning. Keep in mind that, yes, the difference in resistance can be minimal when the voltages of lightning are considered. But then again, so is the difference in resistance between a flat open plain, and a person standing on that plain. But lightning _will_ find the path of least resistance, no matter how little difference there is from the surrounding terrain. Of course, the best thing to do is just not build in open, high terrain :-) -- | Bill White Internet: bwhite@oucsace.cs.ohiou.edu | | PAUL'S LAW: | | You can't fall off the floor. |
gill@bnlux0.bnl.gov (ronald gill) (07/23/90)
For those interested in persuing the lightning rod and St. Elmo's fire questions further, go to your library and check out: Malan, D.J., _Physics of Lightning_, English Univ. Press, Ltd., 1963 Uman, M.A., "Some Comments on Ball Lightning", J. Atmosph. Terr. Phys. _30_, 1245 (1968) Jennison, R.C., "ball Lightning and After-images", Nature _230_, 576 (1971).
raoul@eplunix.UUCP (Nico Garcia) (07/24/90)
[Various people discussing the effect of lightning rods drawing or repelling lightning bolts] Gentle folk, perhaps we could settle the question of repulsion/attraction by examining a more basic question: what is a lightning bolt? Is it the massive electrical current between thunderclouds and the earth carried by plasma, accompanied by a lot of noise? Or is it any current carried between thunderclouds and the earth large enough to create visible effects or carry measurable current? If I remember correctly from *my* old physics instruction, the lightning rod acts to dissipate the electrical potential before the strike happens. Much like doing your work on an anti-static pad, the slight conductive path it provides dissipates local concentration of electrical potential energy and prevents sparks between electrically isolated systems when brought into contact (such as a thundercloud and the earth connected by a column of rain-filled air.) So if there is a strike nearby, since the damn things tend to be at the top of buildings in the open and at ground potential, it'll happen there. But the chance of a nearby strike is much less, so they are effective protection. The effect is much like putting a needle into a water balloon: left there, it drains the pressure before the system ruptures. Yes, that is where the system is likely to break down. But frankly, if I lived in a wooden building (which I do), I'd much rather the lightning hit a big conductor tied to the pipes and drain to ground than let it bust open my roof and light my attic on fire. -- Nico Garcia Designs by Geniuses for use by Idiots eplunix!cirl!raoul@eddie.mit.edu
kimf@arrester.caltech.edu (Kim Dorian Flowers) (07/25/90)
richard@locus.com (Richard M. Mathews) writes: >Here's the real scoop (source: The Feynman Lectures on Physics, Vol 2, >chapter 9). Away from thunderclouds, the earth has a negative charge >relative to "the sky." The potential difference is quite incredible: >about 100 volts per meter. Why does this not electrocute you? Because >your skin is so much better at conducting than air, your skin can be >treated as a perfect conductor. Your head and your feet have the same >potential as the earth. A foot from your nose, the air is at a potential >of +200V. Anyway of hooking up to this potential difference and drawing some energy from it? :) Kim Flowers
grayt@spock (Tom Gray) (07/25/90)
In article <1047@tsdiag.ccur.com> davet@tsdiag.ccur.com (Dave Tiller N2KAU) writes: >In article <1990Jul19.210925.165@mlb.semi.harris.com> sjohnson@gumbee.mlb.semi.harris.com (Scott Johnson) writes: >- >- >-I, however, have heard enough of this nonsense! I didn't study E-mag and >-solid state physics this long to still be able to swallow these lines! >- >-I think maybe this 'lightning rods repel lightning' stuff was started as >-a cruel textbook joke to baffle physics students by some screwed up prof. >- >-CAN ANYONE COME UP WITH A REFERENCE? >-SURELY IF THIS 'STRANGE BUT TRUE STORY' IS FACT, THEN IT'S DOCUMENTED. >-i'D LIKE TO GET TO THE 'THEORY' BEHIND WHAT I CONSIDER VICIOUS >-RUMOURS ABOUT MY FAVORITE 'FIELDS'. :) > >Popular Mechanics had an article on lightning protection for mountaintop >antenna installations. It used giant mushroom shaped wire mesh structures >to avoid the point charge buildup so the lightning would hit the mushroom, >_not_ be deflected toward the antenna tower. Unfortunately I can't provide >the chapter and verse, since it's been a few years, and my Pop Mechs are in >Va. Anyone else read this article? >-- The July 1990 issue of TE&M magazine contains an article describing the latest thinking in lightning protection. It confirms that a space charge does build up around a lighning rod which reduces its efficency. A lightning leader must make a closr approach to the rod to trigger the upward intercepting leader to complete the ground cloud path for the bolt. Another contributer mentioned the use of heavy guage wire to conduct the down current from the rod. As you might expect for currents with such fast rise times and magnitude things are not that simple. There is massive amounts of capacitive coupling from the down conductor to the buildoing structure. This will cause the structure to rise in potential with the down conductor. This may not be bad since it causes electrical equipment to rise in in potenetial with their surrounding and cabling which can prevent destructive breakdowns. Lightning protection is a matter for specialists and I am certainly not one.
cage@fmeed1.UUCP (Russ Cage) (07/25/90)
In article <kimf.648884649@arrester> kimf@arrester.caltech.edu (Kim Dorian Flowers) writes: >richard@locus.com (Richard M. Mathews) writes: >>chapter 9). Away from thunderclouds, the earth has a negative charge >>relative to "the sky." The potential difference is quite incredible: >>about 100 volts per meter. >Anyway of hooking up to this potential difference and drawing some >energy from it? :) Yes. An ion source (whether radioactive or merely a corona point) will conduct micro-amp to milli-amp currents into the air, depending on the configuration. You need to put it high up. The problem is using this energy: it is extremely high-voltage and low-current. You are dealing with a source impedance of megohms to gigohms. I have seen propotypes of electrostatic motors to convert this electricity directly to work. They are... different. The supply is definitely dangerous, and can spark over a good part of an inch. Protecting the collection system from lightning is problematic. This was pretty hot stuff in the alternate-energy school of thought a while back, but it's pretty cool now. The technical problems seem to be more than just slightly hard to solve. -- Russ Cage Ford Powertrain Engineering Development Department Work: itivax.iti.org!cfctech!fmeed1!cage (Business only) Home: russ@m-net.ann-arbor.mi.us (Everything else) I speak for the companies I own, not for the ones I don't.
grege@gold.GVG.TEK.COM (Greg Ebert) (07/26/90)
>>Your head and your feet have the same >>potential as the earth. A foot from your nose, the air is at a potential >>of +200V. > >Anyway of hooking up to this potential difference and drawing some >energy from it? :) > Er, um, it depends upon how determined you are. I read, perhaps in Scientific American , that there is a current density of 1000 amps/sq mile over the surface of the earth, but I don't recall what the weather conditions were; I would presume it would be during an impending electrical storm. That figures out to ~40uA/sq foot, unless you happen to be 'lucky' enough to snare a lightning bolt. The same article mentioned that NASA has measured the current of several bolts which struck launch towers to be up to 30,000 amps (OY !!). I had an insulator from a 16KV power line which had an unusual melted spot on the mounting flange, like someone heated it with a torch and let the molten metal 'run' a bit. I've always wondered if it was from a lightning strike. Has anyone ever seen lightning strike the ocean ? Must be rather trippy...
bldrnr@Apple.COM (Brian Hurley) (07/26/90)
Someone asked about lightning strikes over the ocean. My dad has this one in a millon photograph of lighting striking a pillar of water that was thrust up by a depth-charge. The sky was clear, it was in full daylight, and there was not a cloud in the sky. The top third of the pillar was incandesent where the bolt entred. The film was WAY over exposed along the path of the bolt, but ther was no glare. Makes the bolt look as if it was a solid object protruding out of the column of water. Some where in storage I have this TimeLife book on weather, containing very general topics on weather with lot's of cool pictures. The book has a large section on lightning, and pictures that will raise the fur on the back of your neck! - Brian ----------------------------------------------------------------------------- / --/--bldrnr--> Apple Computer Inc. 10500 N. De Anza Blvd, Cupertino, CA. \ \ Disclaimer: No warranties are expressed or implied PERIOD! / / Whatever I say, >>I SAY<< keep my employer out of it! \ \ / / UUCP: bldrnr@apple.UUCP CSNET: bldrnr@apple.CSNET \ \ ARPA: bldrnr@apple.apple.COM / -----------------------------------------------------------------------------
tmp@doc.ic.ac.uk (Trevor Peacock) (07/27/90)
kimf@arrester.caltech.edu (Kim Dorian Flowers) writes: > > Anyway of hooking up to this potential difference and drawing some > energy from it? :) > > Kim Flowers Well, I seem to remember reading how experimenters in the early days obtained their high voltage supplies from insulated wires held aloft on poles and strung across the countryside. The end of the wire was brought into the lab and connected to a metal sphere to hold the charge. There was mention that the charge increased significantly when it was snowing. I haven't tried this - my garden is a bit too small :) I think the book was called "the man who was frankenstein" or something like that. Trev..
amaranth@vela.acs.oakland.edu (Paul Amaranth) (07/27/90)
> Anyway of hooking up to this potential difference and drawing some > energy from it? :) There was an article in popular science quite a few years ago (20?, alright a LOT of years ago) about electrostatic motors that could be driven from ^^^^^^^^^^^^^ the potential difference. The idea being you could use a helium balloon to get up to a potential of a few KV. Note these are not ordinary motors. It was a neat article, they had cars running on these things and everything. (Maybe they really had an anti-gravity device in there 8-). I have never seen one of these devices myself. I would think there would be a problem getting sufficient current to do useful work. Probably could make a toy motor run (Don't do it during a lightning storm!) Not to get off the track too much, but I had a lighting strike close (*VERY* close) to my house. I was lying in bed watching tv when the windows went white immediately followed by the BOOOM. After peeling myself off the ceiling (THATS the secret of anti-gravity ;-) I went to look at the damage: All my computer equipment was slagged (so much for surge protectors - they don't work at ground zero) as well as some audio equipment and my answering machine. My $5 digital clock survived unscathed. Despite intensive investigation, I never found an indication of where, exactly, it hit. -- Paul Amaranth office: (313) 370 4541 home: (313) 650 2428 (internet) amaranth@vela.acs.oakland.edu | Always remember -- That (bitnet) amaranth@oakland | way, when somebody asks (uucp) ...!uunet!umich!vela!amaranth | you'll know - J. Carson
jboggs@inco.UUCP (John Boggs) (07/30/90)
In article <2253@vela.acs.oakland.edu> amaranth@vela.acs.oakland.edu (Paul Amaranth) writes: > >Not to get off the track too much, but I had a lighting strike close >(*VERY* close) to my house. I was lying in bed watching tv when the >windows went white immediately followed by the BOOOM. After peeling >myself off the ceiling (THATS the secret of anti-gravity ;-) I went A friend and I got caught out on the river in one of our recent afternoon thunderstorms. We had holed up in the cabin waiting it out as the rain and lightning and thunder came down all around us. I was sitting in the cabin leaning against an ungrounded aluminum trim strip. My friend was lean- ing against an ungrounded aluminum strip which holds the weather boards in place. A particularly close lightning strike set up some kind of charge in those ungrounded pieces of metal that was sufficient to shock both my friend and I simultaneously. Neither of us received enough of a shock to cause any damage but I can tell you we kept away from metal parts for the rest of the storm. Any explanations of how this occurred? As far as we can tell, the lightning did NOT strike any part of the boat directly. -- John Boggs McDonnell Douglas Electronic Systems Company McLean, Virginia, USA
davet@tsdiag.ccur.com (Dave Tiller N2KAU) (07/31/90)
In article <2139@gould.doc.ic.ac.uk> tmp@doc.ic.ac.uk (Trevor Peacock) writes: - - kimf@arrester.caltech.edu (Kim Dorian Flowers) writes: -> -> Anyway of hooking up to this potential difference and drawing some -> energy from it? :) -> -> Kim Flowers - -Well, I seem to remember reading how experimenters in the early days obtained -their high voltage supplies from insulated wires held aloft on poles and strung -across the countryside. The end of the wire was brought into the lab and -connected to a metal sphere to hold the charge. There was mention that the -charge increased significantly when it was snowing. - Amen to the increase in static potential when snowing!! I got the BeJesus shocked outta me when I reached over to tune my 10m Amateur radio whilst traveling on a _metal_ suspension bridge (Del. Mem). I figured at the time the snow added to the static buildup by imagining all of those snowflakes hitting my antenna and losing electrons as they slipped past. Ouch!!! -- David E. Tiller davet@tsdiag.ccur.com | Concurrent Computer Corp. FAX: 201-870-5952 Ph: (201) 870-4119 (w) | 2 Crescent Place, M/S 117 UUCP: ucbvax!rutgers!petsd!tsdiag!davet | Oceanport NJ, 07757 ICBM: 40 16' 52" N 73 59' 00" W | N2KAU @ NN2Z