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A lightning bolt would be worth only about a nickel (2015)

engineering.mit.edu

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Re: A lightning bolt would be worth only about a nickel (2015)

#61

Post by elif »

sebzim4500 wrote: post #56
usrn wrote: post #51

Earlier quoted context omitted.

I know a number of people who have been struck by lightning. It seems like you've got a decent chance at survival if you're not touching anything metal.

Do you know a lot of people who stand on top of tall towers during storms? Otherwise, unless you know tens of thousands of people there is very little chance of knowing multiple people who have been struck by lightning.

I also know two people, my mother and a leader at my boyscout camp. Both wearing rubber-soled shoes and survived without needing hospitalization.

Maybe birthday paradox or something similar at play? Only 64 commenters but appears more common than your belief would indicate.

I bet if you are a regular golfer you would know more, and if you spend 100% of your time in a concrete jungle you would know less.

Re: A lightning bolt would be worth only about a nickel (2015)

#63

Post by themitigating »

andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

The typical house has 240 volt service in the US (two legs of 120v). I would also say a decent number of homes have 200amp as well

Re: A lightning bolt would be worth only about a nickel (2015)

#64

Post by greenbit »

andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

Idk, I think OP indicated that a typical lightning bolt would power a typical house (presumably at the stated nominal full load) for about 15 minutes. I.e., you'd need 4 strikes per hour, per hour. Now granted most houses won't run at peak load all the time, maybe you'd only need one strike per hour per house - but that's still clearly a lot more lightning than is generally seen.

Re: A lightning bolt would be worth only about a nickel (2015)

#65

Post by samatman »

themitigating wrote: post #63
andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

The typical house has 240 volt service in the US (two legs of 120v). I would also say a decent number of homes have 200amp as well

This is true, but I'm fairly certain that the amps of available power are calculated on a 120v basis, a 10 actual-amp washing machine would use 20 accounting amps at maximum power.

Re: A lightning bolt would be worth only about a nickel (2015)

#67

Post by greenbit »

david_draco wrote: post #62

Therefore, one could easily generate lightning with equal destructive power? Why is it not used yet in war (airplane to ground) or for entertainment (airplane to airplane)?

A megajoule in a microsecond, that's a terawatt impulse with decidedly RF personality. Anything that could generate that would be as big as anything that could capture it. Not exactly nimble enough to weaponize.

Re: A lightning bolt would be worth only about a nickel (2015)

#68

Post by photochemsyn »

Fun facts & questions from Feynamn lectures:

> "On an ordinary day over flat desert country, or over the sea, as one goes upward from the surface of the ground the electric potential increases by about 100 volts per meter. Thus there is a vertical electric field E of 100 volts/m in the air. The sign of the field corresponds to a negative charge on the earth’s surface. This means that outdoors the potential at the height of your nose is 200 volts higher than the potential at your feet! You might ask: “Why don’t we just stick a pair of electrodes out in the air one meter apart and use the 100 volts to power our electric lights?”

> "Although the electric current-density in the air is only a few micromicroamperes per square meter, there are very many square meters on the earth’s surface. The total electric current reaching the earth’s surface at any time is very nearly constant at 1800 amperes. This current, of course, is “positive”—it carries plus charges to the earth. So we have a voltage supply of 400,000 volts with a current of 1800 amperes—a power of 700 megawatts! With such a large current coming down, the negative charge on the earth should soon be discharged. In fact, it should take only about half an hour to discharge the entire earth. But the atmospheric electric field has already lasted more than a half-hour since its discovery. How is it maintained? What maintains the voltage? And between what and the earth? There are many questions."

https://www.feynmanlectures.caltech.edu/II_09.html

Re: A lightning bolt would be worth only about a nickel (2015)

#70

Post by samatman »

andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

The kWh is of course exactly what you want if you're working with power over time.

Example: a 100 amp house circuit running maxed out in the US will use 12 kWh per hour, or 0.2 per minute. Try doing it in your head with joules. Annoying right?

12 kWh / h? Am I a crazy person? No. I'm working on a useful problem.

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