So today in Famous American we studied Benjamin Franklin. We studied all the different things he invented and all the thing he did in his life. I think him inventing glasses is pretty cool. So is the lightning-rod! This makes me wonder how much electricity is in a lightning bolt. He also invented a new type of fire place and chimney. He's so cool that he has a couple of scientific institutions named after him!
What's also cool is that he was home-schooled. His father could only afford two years of school for him, so after that he taught himself everything he needed to know.
Finally he's cool because he pretty much invented the way we do the post office. They had mail before him, but he created a system and a governmental department to take care of it. I wonder how many stamps the Post Office has for Benjamin Franklin?
5 comments:
Franklin is very interesting. Is there a biography of him at the library? I think you would enjoy reading about him.
Why don't you look in wikipedia about lightning and let me know how many volts are in a lightning bolt.
Lightning can occur with both positive and negative polarity. An average bolt of negative lightning carries an electric current of 30,000 amperes (30 kA), and transfers fifteen coulombs of electric charge and 500 megajoules of energy. Large bolts of lightning can carry up to 120 kA and 350 coulombs.[15] An average bolt of positive lightning carries an electric current of about 300 kA — about 10 times that of negative lightning.[16]
The voltage involved for both is proportional to the length of the bolt. However, lightning leader development is not just a matter of the electrical breakdown of air, which occurs at a voltage gradient of about 1 megavolts per metre (MV/m). The ambient electric fields required for lightning leader propagation can be one or two orders of magnitude (10−2) less than the electrical breakdown strength. The potential ("voltage") gradient inside a well-developed return-stroke channel is on the order of hundreds of volts per metre (V/m) due to intense channel ionization, resulting in a true power output on the order of one megawatt per meter (MW/m) for a vigorous return stroke current of 100 kA.[17] The average peak power output of a single lightning stroke is about one trillion watts — one terawatt (1012 W), and the stroke lasts for about 30 millionths of a second — 30 microseconds.[18]
Lightning rapidly heats the air in its immediate vicinity to about 20,000 °C (36,000 °F) — about three times the temperature of the surface of the Sun. The sudden heating effect and the expansion of heated air gives rise to a supersonic shock wave in the surrounding clear air. It is this shock wave, once it decays to an acoustic wave, that is heard as thunder.[18]
Can Old Guy explain what this means to me?
I don't know about old guy, but it makes me wonder if Marty makes it home.
Have you ever seen the movie "Back to the Future"? In it, a teenager named Marty is accidentally sent back in time to 1953. Unfortunately, the time machine he was in ran on plutonium and he hadn't take any with him so he couldn't get back. He knew that it took 1.21 Gigawatts (1.21 billion Watts or 1,210,000,000 Watts) of electricity to power his time machine and send him back home - but that much power is impossible to generate without an atom bomb - or maybe a bolt of lightning.
But would he really be able to get that much power from a bolt of lightning? Or were the guys who wrote the movie just making numbers up?
There is over a trillion Watts of electricity in a bolt of lightning - but that power is spread out over the entire length of the lightning bolt. Only a small amount of that power could really be used by the time machine.
Watts = Volts X Amps.
The article said that air conducts electricity if the voltage gets above about a Megavolt per meter (1,000,000 Volts per meter). If the "flux capacitor" (his time circuit) is only 3/10 meter in size, this means that the most he could get is 3/10 of a million volts (maximum) of electricity through the time circuit before it started blasting through the air instead of through the "flux capacitor". If an average negative lightning bolt hits Marty's car with about 30 kA (30 Kiloamps or 30,000 Amps) - does Marty make it home?
So he needs 1,210,000,000 Watts and he has 300,000 Volts and 30,000 Amps. Since Watts equals Volts times Amps - will he really have enough power?
Jonathan - thanks for looking up these numbers! I've never taken the time to figure this out before!
Well Bob, the answer is of course yes. Because you showed me the first movie when you came over last time...and I noticed that there are two more. If he can't make it home than there can't be any more movies. :p I'll try to have dad help me do the math to see if he can actually make it back, but my guess is math-wise he's screwed.
He he. Good logic.
Still, maybe he filmed movies 2 & 3 in 1953 because he couldn't get back! After all, you haven't seen 2 or 3 yet ;)
Come on, Jonathan! Be like Doc Brown and do the math! Or at least make a model :)
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