Arcing during lightning despite “low” voltage?
Hello everyone,
I sometimes ask myself strange things and often cannot explain them.
Normally, I'd Google it. This is another one of those questions where I don't know how to Google it, because none of the questions actually answer my question.
I understand that a voltage of approximately 1000V is needed for electrons to bridge 1mm of air to form an arc. I'm also aware that once the arc is formed, the voltage can be lower and the arc will still be maintained.
I often find online that lightning that reaches the ground has a voltage of around 100,000,000V (0.1 GV). I also find online that a lightning bolt (the distance it has to travel through the air before reaching the ground) is on average 6km (or 6,000,000mm) long.
Now you can probably already *deduce the question (ha, pun!)
If 1,000V are needed to bridge 1mm, why does lightning need 100 million volts to bridge 6 million millimeters?
Actually, he would need at least 6 billion volts…
I wouldn't be aware that a higher current would help convert lower voltage current into an arc.
Even if the rain occasionally forms a conductor, the air gaps between the individual raindrops are still significantly wider than the lightning with 0.1GV.
Thanks in advance for your answers! 🙂
(2 votes)
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In thunder flashes various things are added. Local field strengths or Concentrations of charges which are dependent, inter alia, on the humidity.
With a flash, extremely many charges move within a thin channel, i.e. we have a very high current density and the temperature of this thin channel rises at extreme heights. This in turn ionizes the air in the environment and the channel becomes more conductive. At the end of the process, this process swings up until the lightning strikes the earth and the quantities of cargo have settled again.
The length of a cloud earth flash varies from about 1 km to 3 km. High atmosphere flashes (“cobbles” or “Elven”) can be over 50 km long. (The lower the pressure, the easier can shock ionization take place)
An exact answer to the question is still the subject of research. However, it is known that the humidity and low pressure greatly reduces the necessary voltage for a cloud earth flash. A lightning does not emanate from a fixed position as in the laboratory, but the charges are distributed in a cloud. These space charges presumably ensure that the air becomes partially conductive and only then the actual lightning strike occurs. The lightning may be induced by cosmic radiation. Pre-discharges occur before the actual main flash (note: Elmsfeuer). Therefore, the measured voltages of about 200000 volts/m for flashes between clouds are, in terms of size, smaller by about 10 than the measurements in the laboratory.
The cloud earth flashes distinguish between negative flashes and positive flashes. In negative flashes, the underside of a cloud is negative and positively charged in positive flashes. Positive flashes are much more rare than negative flashes, but have a multiple current strength such as negative flashes.
In
https://de.m.wikipedia.org/wiki/Blitz
there’s a lot in it, too:
ANNEX A lightning discharge is significantly more complex than a pure spark discharge. The physical laws on which natural lightning is based have not yet been investigated. ‘>
The distance zw. Cloud and earth, as you already wrote, is too large for a single-stage discharge. Thunderstorm flashes build up in steps, before the discharge, a channel of ionized air, so to speak, allows a conductive path where the actual discharge takes place. And this also not in a “slip” but gradually in a very fast sequence. They’ve been researched with high-speed cameras.