# Tag Info

15

1) yes, it basically will find a non-optimal solution. At every point, the top of the ray looks for the bigger potential gradient, the charge in the surrounding volume grows, polarizing surrounding material (air, in this case) until a bigger gradient shows up and the ray continues over that direction. This is why the lightining path looks like a jigsaw; its ...

10

In fresh water what makes lightening so dangerous to a swimmer is that most of the current travels on the surface of the water, so rather then getting a $1/r^2$ falloff in current density, you see a $1/r$ falloff. Obviously eventually it will be conducted down into the mass of the water, but this takes a many meters. In salt water, this should happen much ...

8

Here's a crude way to look at the problem: Suppose there are $N$ wires. Each has resistance $R$, common potential difference $V$ and are connected in parallel. So the current through each wire is $I = \frac{V}{NR}$. Let's imagine a hypothetical wire formed by sea water which has a length, $L$ and cross sectional area, $S$. There are approximately ...

8

I have always assumed it could be put down to a small set of causes: The stroke may have a physical extent and geometry that leads to a perceptible duration between the arrival of the sound due to the near part of the strike and that due to the far part. That is, what Georg said. If the geometry of the terrain is right you may be hearing echos off of cliff ...

8

AM radio typically transmits at around 1 MHz, FM radio at about 90 MHz. Measurements of the RF spectrum of lightning strikes show a falloff with frequency of about 20 dB per decade in that frequency range, so with FM about 2 decades above AM, you'd expect AM to have about 40dB higher interference from a lightning strike. In addition to that, FM signals ...

8

At sufficiently high voltages almost everything conducts due in part to quantum tunneling of electrons. An insulator has a breakdown voltage which is the field strength required before it will start conducting. Related to the breakdown voltage is the dielectric strength which is the minimum voltage over distance ($\mathrm{V}/\mathrm{m}$) before a material ...

6

Basically: no cheap, efficient, large-scale battery technology exists. This question gets asked in the world of intermittent renewable energy generation all the time, but it is even harder for lightning because of the extermely high power of the energy burst, so that's an extra problem to solve on top. Also, how do you predict where it will strike? Build a ...

6

In answer to your second question: "Now going with my b) reasoning, wouldn't you be just as safe standing next to a giant conductive pole (i.e. a lightning rod)? Wouldn't the lightning just go through the lightning rod and you'd be 100% safe?" No. A lightning strike can carry a high current, up to 200 kiloamps has been recorded. Not only can the current ...

6

Electric Conduction: At atmospheric pressure, air and other gases are poor conductors (Insulators) of electricity. 'Cause they don't have any free electrons to carry current. But, once free electrons are produced in gas by ionization (They become plasmas), discharge of electricity through gases appears. This could be done in many ways such as applying large ...

6

The majority of the energy is dissipated in the travel through the air from the cloud to the ground. The energy goes into heating the air and generating the shockwave that we hear as thunder. I can't give you a single definitive refernce for this, but Googling "energy dissipation lightning" will find lots of relevant articles. You can understand why this is ...

5

Yes, if it is not a plastic covered car it is an effective Faraday cage. If the tires are such that the car is insulated electrically, if it is hit it will take some time to discharge to the ground, but still the passengers would be safer than standing next to it outside. I have learned that modern tires are particularly constructed so that the static ...

5

The wikipedia article is quite good on this subject. For any discharge in the air the molecules of the air must be ionized. This ionization happens during thunderstorms because of the high static electric fields carried by the clouds which generate "streamers", i.e. paths for the electrons to flow downwards. Corresponding streamers are formed by conductors ...

4

This is because the different parts of a stroke are be very different in distance. This Reverberations and echoes of sound last longer than those of light. is obviously wrong. Which walls or mountains are the reflectors of those echos? Which rooms do the reverberations?

4

A lightning bolt produces hot gasses (30,000 °C). This results in very high pressures. This pushes away surrounding material. When the material cools, the empty region where the current passed is left empty for the same physical reasons that a piece of wood retains the imprint of a nail. Some of the sand is melted and solidifies before it can flow back into ...

4

This video illustrates how a candle flame conducts a high voltage (10,000 volts). Although the ion density is small in a candle flame, they are sufficiently present to conduct electricity.

3

Tesla investigated the possibility of using the potential built up in the atmosphere. It's not clear how far he got with this. In principle it's possible, but in practice it doesn't seem likely anyone could make it economically viable. You would need to build a large capacitor with one side grounded and the other positioned up in the clouds where ...

3

Rather than attempting to capture the energy of lightning, think about capturing the energy of the separated charge before lighting discharges the stored energy. Find a way to convert the electrical energy of naturally separated charge in the atmosphere into useful work... Galt's motor if you will allow.

3

I have seen a presentation in a lab recently, from a group working precisely on the simulation of lightning. I was surprised to see, at a small scale, how crooked and twisted on itself, was the path of the lighting, due to retro-action of the magnetic field, created by the current, and the varying electric field, on the path itself. The path ends up rolled ...

3

The 3D shape of the lightning channel over many kilometers of extent can be teased out of three simultaneous sound recordings made from three different spots. The coding is similar to that which produces CAT scans, very abstruse, lots of matrix algebra. Similar systems are used to localize gun shots in urban areas using microphone networks.

3

Why does it radiate? You want an explanation on a sub-atomic level? Well then, rather than look to the fact that lightning makes the air 'hot' (of course it does), what you really need to know is this: whenever an atom changes energy level (which outside of nuclear reactions means an electron jumps from one orbital to another at a different energy level), it ...

3

A very interesting question, especially because of the discussion that it spawned. All the answers here seem to revolve about two different mechanisms: thermal radiation of the 50.000K plasma radiation due to recombination of the resulting plasma It's not very easy to find authorative sources on either, but googling for "spectrum of lightning" turned ...

3

It is difficult to measure, but a bulk of it's energy is not spent in ionizing the atmosphere or in the sound wave but in the movement of charge itself. However lightening labs will measure a variety of factors to characterize the strike. They launch small rockets carrying a small wire or sometimes emit some conductive ionized gas which triggers a strike ...

3

It depends on how you define "lightning". When electrons flow from clouds to the earth, ionizing the air and producing light, does your definition include the electrons, the air, the plasma, the light, or a subset? Pedantically speaking, I would say that lightning is the flow of electrons, and to me a flow is an abstract idea (the action of moving in a ...

2

either: it comes down very close to you, so the lightning will probably go through your head and fry you or: it comes down some distance away and dissipates rather quickly. salt water is probably even more conductive than your body, so the current might even flow right around you. I doubt it would make much of a difference. the danger from thunderstorms ...

2

The quotes you give do not really explain much. With a conductor one can short the static field of the atmosphere, one does not need oscillations for that. I think it was Benjamin Franklin with reaching the clouds who discovered that first hand? Lightening strikes when naturally induced upward leaders reach and meet the charged cloud downward leaders ...

2

2013 costs of kWh are about .16 cents. I've read that a lightening strike generates approximately 8kWh. The profit from selling this captured power would be about \$1.28. Tell me where I am wrong. As far as converting the strike into power that is easy and can be done with existing technology. Direct the strike into a container of noble gases. Power ...

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