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About Lightning

by beluluk
Tags: lightning
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beluluk
#1
Apr18-06, 08:52 AM
P: 27
When i was learning electronic stuff on the site, i found this... perhaps somebody could help the webmaster.

http://www.williamson-labs.com/lightning-motion.htm

i've got no idea.
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dav2008
#2
Apr18-06, 12:26 PM
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Maybe the car was accumulating more charge as it went faster?

That's just a wild guess.
Danger
#3
Apr18-06, 01:07 PM
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Peculiar. I really don't know either, but I'm wondering if the antenna happened to be tuned to the sort of frequencies most powerfully emitted during a lightning strike. If so, could the induced current from the RF have been enough to cause it? Perhaps also the static charge, as dav2008 suggested, increased with greater speed through the air. Might that then have served to fine-tune the antenna even more?
I really hope somebody has the right answer for this, because now my curiosity is piqued.

tehno
#4
May13-06, 08:10 AM
P: 363
Cool About Lightning

Quote Quote by Danger
Peculiar. I really don't know either, but I'm wondering if the antenna happened to be tuned to the sort of frequencies most powerfully emitted during a lightning strike. If so, could the induced current from the RF have been enough to cause it? Perhaps also the static charge, as dav2008 suggested, increased with greater speed through the air. Might that then have served to fine-tune the antenna even more?
I really hope somebody has the right answer for this, because now my curiosity is piqued.
I think that current induced from lightning RF isn't the only cause, but also the static magnetic field of a powerful lightning current (~100,000 A).
Faster the car drives through the field more electricity it generates (Faraday-Lenz law?).
Just a thought I find worth considering of.
Danger
#5
May13-06, 12:52 PM
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I don't know enough about electricity to judge that, but it sounds plausible. I'm just wondering why it would spark, though. Wouldn't the whole vehicle, including the antenna, have the same charge?
tehno
#6
May13-06, 01:19 PM
P: 363
Well,the author who described his experience didn't gave enough data about "electric circuitory" circumstances so I can't tell.
But to generate difference of potential via magnetostatic induction responsible for igniting a small spark ,as described, one must have sort of open "loop".
IMHO,electrostatics causes (Electrical field induction ) were first to be blamed for, weren't he mentioned dependece of spark intensity on car speed.
RandallB
#7
May13-06, 02:02 PM
P: 1,545
I'll send Glen an Email to let him know his ears should be burning and let him in an a couple ideas here:

Based on the info from Glen's truck trip, some comments that may apply:

First consider a generator – the wire windings turn inside a magnetic field to generate electricity at the armature. BUT if you were to reorient the winding of the wire by 90 degrees you would not cross the fields in a way to create any electricity at all.
- Look at the magnetic field growing and collapsing from the vertical lighting bolts as the movement of the M field seen from the wire view. And when stopped the non moving antenna being like the wire coiled turned in the wrong direction to generate electricity.

- Now as you move faster and faster in the truck one of two things, maybe a little both.
1) First, the Probe (antenna) is moving is a new direction across the generated magnetic field generating a stronger effect with higher speeds.
2) Second, the Probe is being blow over at a new angle (it is a whip antenna right), for a different (and increasing with speed) probe angle against the magnetic field being tested.

Likely need some additional controlled field tests to decide which may be important.
Seems reasonable to me – Ever considered duplicating the event to get more data?
NoTime
#8
May13-06, 10:20 PM
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The little ball on the end of a whip antenna has a purpose besides the obvious one of keeping people from impaling themselves.
Apparently a moving vehicle builds up a static charge, not unlike a Van de Graaff generator.
They found years ago that without the ball to spread out charge a sharp point on the antenna will arc off and cause static in the radio even without any lightning around.
Of course the rest of the charge on the car is going to want to follow out through this discharge path.
So I would imagine that the combination the static charge from moving plus whatever the lightning induces makes the antenna arc off anyway.
tehno
#9
May15-06, 12:32 PM
P: 363
Quote Quote by NoTime
The little ball on the end of a whip antenna has a purpose besides the obvious one of keeping people from impaling themselves.
Apparently a moving vehicle builds up a static charge, not unlike a Van de Graaff generator.
They found years ago that without the ball to spread out charge a sharp point on the antenna will arc off and cause static in the radio even without any lightning around.
Of course the rest of the charge on the car is going to want to follow out through this discharge path.
So I would imagine that the combination the static charge from moving plus whatever the lightning induces makes the antenna arc off anyway.
NoTime,I think you hit the nail right in the head!
Reconsidering it all over again,and having in mind what you said ,I'm 99% sure it must be a combination of electrostatics and sudden lightning.
Lightning serves just as a trigger .
During the fine weather a vertical electrical field on the ground level atmosphere is about 50-100 V/m .During the storm weather the magnitude of that field rises to 10,000V/m or more.
When lightning occurs ,the ambient field quickly drops down,leaving induced and previously accumulated charge on "its own".The transients take place.
Also,the faster car drives more charge via electrophoresis action can be acquired,particularly if it drives through air with electrified molecules & particles present below a thunderstorm.
RandallB
#10
May15-06, 05:11 PM
P: 1,545
At first I doubted the idea of seeing the antenna as a static ground lead, (like the tabs with frayed pointed ends attached to the trailing edges of airplanes to ground DC static charge build us into the air). Remember the antenna glen has described is not electrically attached to the truck as can be seen in his diagram it was disconnected from the radio. This would seem inconsistent with explanation proposed by NoTime where we basically have Direct Current movement of larger or smaller amounts of charge build ups; much like static from walking across carpeting. Where I prefer to think of high energy AC from the individual bolts more like a spark igniting a high energy flux though a Tesla Coil.

However, as we must take the role of the theoreticians;
And Glen his with truck as our experimentalist;
We must decide how much we trust the completeness and detail of his observations.
Taking particular note of Glen’s following observations:
The more severe the lightning strike, the bigger the arc;
the faster I drove, the brighter the arcing.
Should we trust that our observer here is giving use information that “the bigger the arc” and “the brighter the arc” are actually two different things being observed in different conditions and are correctly giving us valuable information about the problem.

If we do trust our observer we could conclude that both solutions apply as follows:
1) The stronger or closer lighting bolts – when detected by our antenna probe – was giving a “bigger arc” based on the stronger RF AC energy being observed at the end of the antenna lead.
2) Once the High Voltage & Frequency arc spans the connector being observed in our little test, a path of ionized air provides a path to the coax ground. Since the coax is grounded to the skin and frame of the truck any DC accumulated charge in the truck now has a path to ground out to the air via the antenna probe; Explaining the “brighter arc” observations.

RF AC arcing forming the “triggering” path of varying “size”, with a simultaneous DC arc following that path contributing to the observed “brightness” of the combined arc.

Have to give a lot of credit to some very good and detailed observations by our experimental observer Glen for a good job on reporting the observations.
Maybe we as theoreticians should recommend some additional simple tests that could be preformed by the same truck (laboratory) if another similar storm should come along for our “Lab Guy” to try out and report back on. Not that we can really hope to get additional data.
tehno
#11
May16-06, 01:45 PM
P: 363
Quote Quote by RandallB
. Remember the antenna glen has described is not electrically attached to the truck as can be seen in his diagram it was disconnected from the radio. This would seem inconsistent with explanation proposed by NoTime where we basically have Direct Current movement of larger or smaller amounts of charge build ups; much like static from walking across carpeting. Where I prefer to think of high energy AC from the individual bolts more like a spark igniting a high energy flux though a Tesla Coil.
RandallB,it's not inconsistent with NoTime's suggestion becouse he didn't talk about full explanation,but mentioned just the dependence of accumulated charge on car speed.And the fact that antenna was not galvanically attached to the truck and disconnected from the radio actually goes in favour of the hypotesis!
As I see it,lightning always induces EM RF disturbances in the pick up antenna but it wasn't a enough to overcome the gap spacing by itself.
It acts like a "trigger" only when additional electrostatic charge is build up
via electrophoresis action as car drives.
So,it's must be a superposition of two effects .
BTW,what's a Tesla Coil,a supermagnet?
1 Tesla is a high magnitude of magnetic field.I doubt the lightning at a distance of a mile could create such fields.
RandallB
#12
May16-06, 06:35 PM
P: 1,545
Quote Quote by tehno
what's a Tesla Coil
You know Tesla
- Inventor of the Radio,
- Wanted to transmit energy without wires in the air.
- Gave up his rights to AC current for next to nothing.

Just google "tesla coil" for some photos of what a small version of his "transmitter" would look like. (Even some Ebay links if you want to build one.)

On a clear Wisconsin evening a large 15 foot one arcing into the air generated enough RF energy to be picked up by a 10 foot tall one in the back of a pickup about 2 miles away with enough power to brightly light up a standard florescent tube.

I like the idea that the high energy RF arc generated by the lighting is the key to the triggering event, and the DC charge is just following that path.

If you could have been there what creative modifications and procedures would you use to enhance the test to gather more data?
scott1
#13
May16-06, 06:50 PM
P: 459
I think the best way to find out what happend is to do try recreate this phenomenon. It doesn't sound like physics currently doesn't have an good explaintion for this(it happend in the 50's and he still doesn't know). But I think that's highlly to happen
He doesn't enough info for an explaniton(like, type of car, if anything was the car, or if he had an attena).
RandallB
#14
May17-06, 10:43 AM
P: 1,545
I disagree Scott, did you actually review the data provided in the OP link.
I think Glen did an amazing job of detailing the event.

Of course physics can provide an answer, just because some of disagree on the fine detail does not mean physics lacks a good explanation.
Just that we might be wrong in understanding the physics!
I certainly could be wrong in my speculation – I’d expect to be wrong more often than a PHD!

This little example is more a test of us than of physics.
For example; after having the luxury of time to consider the issue, what simple things would you have done, if you had been with Glen at the time?
Maybe something that might help clear up the differences in interpretation.

Recreating the phenomenon to see the same thing doesn’t help, what would you do different other than bringing along an entire physics lab?
beluluk
#15
May19-06, 11:56 AM
P: 27
Looks like everyone is agitated.
I'm sorry that i couldn't be much of a help. I'm still a college student after all. I believe that Mr.Glen would be happy to see your theories so that he could build a comprehendable experiment.
I suggest asking Mr.Glen directly via email about the detailed condition, or perhaps a confirmation of the information completeness, and ask him to post the information on his web.
Bytheway, I don't know when, but it seems that the web had been updated. I've been quite busy lately, so i just don't know when.
tehno
#16
May19-06, 02:06 PM
P: 363
Quote Quote by RandallB
I like the idea that the high energy RF arc generated by the lighting is the key to the triggering event, and the DC charge is just following that path.

If you could have been there what creative modifications and procedures would you use to enhance the test to gather more data?
Well ..to test it ,I think one should measure DC potential of the antenna by electroscope vs. the vehicle speed (dependence) regardless of lightning (but during the storm).
Then to measure RF potentials induced just by lightning for a steady vehicle case.
And compare these two for a start.
tehno
#17
May27-06, 01:06 PM
P: 363
Quote Quote by beluluk
I believe that Mr.Glen would be happy to see your theories so that he could build a comprehendable experiment.
I suggest asking Mr.Glen directly via email about the detailed condition, or perhaps a confirmation of the information completeness, and ask him to post the information on his web.
.
Well beluluk,have you sent Mr.Glen email?
If he wants help & disscusion,I would suggest him signing up for PF .
cmcguire
#18
Dec31-06, 07:05 PM
P: 1
The assumption that the antenna is just a straight wire is wrong. That was demonstrated by Mr. Glenn with his rotating dipole experiment.
What is not mentioned is that almost all of the trucker CB antenna arrangements are short monopoles. In order to make the antenna shorter there is a coil (balun) incorporated. usually about 1/2 way up the whip. So now you have everything needed to generate the spark. A Coil moving through a very strong E-field and a spark gap.
The antenna did not generate a spark when stopped because it was then acting as an E-field sensing device. Not enough voltage to spark. Now move the coil incorporated in the antenna's balun and we have all the parts of a generator based on a fixed E-field. (Most generators work on a fixed B-field.) One or the other must be moving to work.
Kudos on the metal ball on the antenna for static reduction. E-fields form "normal to" or directly out from a metal plate. make a sharp point the the field will concentrate to make the per-unit-area charge equal over the entire object. Lightning rods usually work by "bleeding off" charge through this corona effect without "drawing a spark" less charge in the locality less likely a lightning strike. and if one does occur there is a path to ground that will unusually cause less damage going around the building than through it!


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