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[__ Science __ ] Thunder

WIP said:
Now you're getting into Ohm's law. Voltage by itself is not necessarily deadly. It is the current through the heart that disrupts the beating of our heart. We can withstand pretty high voltage without serious risk (on average). For example, ever get a shock from an engine spark plug? Typical voltage for vehicles from the days of points and condensers was somewhere around 30,000v. I'm not sure about today but based on spark plug gaps I'm guessing 50,000 is not far off. Yet, it is possible for a person to be at serious risk with voltages as low as 110v. Why is that? It has to do with the amount of current that is capable of passing through our heart.

A typical dry human body from finger tip to finger tip has a resistance of about 100,000 ohms. A typical current that is lethal is about 100mA. Using Ohm's law we can do the math to determine the likely lethal voltage given these values. Ohm's law says E=IR where E=volts, I=Current (amps), and R=resistance. With a 100,000 ohm resistance and a lethal current of 100mA (.1A) we can calculate the lethal voltage required.
100,000 x .1 = 10,000v

As you can see by this formula, the higher the voltage, the higher the amount of current that can overcome the resistance. In the same way, as resistance drops so does the amount of voltage required to "push" a deadly current through our body.

The thing is, one must remember that these values are typical and not necessarily always true. There are many variables that affect this such as moisture and other contaminants that can lower our body's resistance. For example, body sweat contains a lot of salt and salt is a conductor which means it lowers our resistance therefore a lower voltage could become deadly. Every body is a little different and each has a different resistance.

The best thing to do is avoid electric shock. Consider this. A typical dc welder only uses about 25 - 35 volts. I dropped a wrench one time on top of a car battery and it welded the wrench to the battery posts in seconds. My reaction was stupid because I quickly grabbed the wrench and dislodged it from the battery. I was very lucky that I didn't burn my hand or the battery didn't explode because lead acid batteries emit explosive hydrogen gas.
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125000v at .0001 amps gaps at .44 or .56 on some cars
 
JohnDB said:
Risking a static discharge on a $2.00 pc board is one thing... taking the same risk with a $200-$2000 board is another.

But sometimes I have seen service guys do just that.
Usually followed by the statement " Huh? I don't understand what's going on. I just replaced that board. It should be working. They probably sent me a bad board or something"
Meanwhile I am silently listening to their rant while in judgement of their stupidity.
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But that's my story, and I'm sticking to it Lol! It is under warranty, right?

I thought I read that lightning strikes from the ground up. Things on the ground are mostly positively charged and storm clouds are negative? Energy flows from positive to negative so goes up.
 
Edward said:
But that's my story, and I'm sticking to it Lol! It is under warranty, right?

I thought I read that lightning strikes from the ground up. Things on the ground are mostly positively charged and storm clouds are negative? Energy flows from positive to negative so goes up.
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I also was taught that lightning travels from ground to sky, but now I'm seeing it's more complicated than that. Apparently the initial leader does travel downward to the ground, but the main strike is upward rising.

As far as current direction, this is a conflict between convention and theory. When a guy named Ben Franklin dicovered electricity, he had to guess which direction it flowed. He flipped a coin and decided it traveled from postive to negative. When physicists later discovered that the flow of electrons was actually from negative to positive, massive amounts of research and electrical drawings depicted current flowing in the wrong direction.

The contradiction exists to the present day. Current direction depends on whether you're talking to an electrician or a physicist. Every good electrical engineer will hand you schematics showing positive-to-negative flow, but he'll do it with a wink of an eye. Physicists sit smugly in the corner knowing they're right, but they'd be pretty smug anyway.
 
Speaking of electrical dangers, I read but don't know if it is true, that you can kill yourself with a 9 volt battery.

As the story goes, a soldier, in some military somewhere, read that you could kill someone by passing the current in a typical 9 volt battery from the finger tip of one hand, to a fingertip of the other hand. So..... being the type of guy he was, he soldered wires to the + and - terminals of a 9 v battery and just to be sure, put little cuts in the tips of each of his index fingers...

Story goes that when he put the respective wires into the respective little cuts, that the current passed through his body, through his heart, and stopped it..

Anyone else hear of this? Anyone who can confirm or debunk it?
 
Jacks Bratt said:
Speaking of electrical dangers, I read but don't know if it is true, that you can kill yourself with a 9 volt battery.

As the story goes, a soldier, in some military somewhere, read that you could kill someone by passing the current in a typical 9 volt battery from the finger tip of one hand, to a fingertip of the other hand. So..... being the type of guy he was, he soldered wires to the + and - terminals of a 9 v battery and just to be sure, put little cuts in the tips of each of his index fingers...

Story goes that when he put the respective wires into the respective little cuts, that the current passed through his body, through his heart, and stopped it..

Anyone else hear of this? Anyone who can confirm or debunk it?
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No,those lack the amps .a Tazer would kill the healthy then abd those put out 40k volts up to 60k .
 
KevinK said:
Ben Franklin dicovered electricity, he had to guess which direction it flowed. He flipped a coin and decided it traveled from postive to negative. When physicists later discovered that the flow of electrons was actually from negative to positive

The contradiction exists to the present day. Current direction depends on whether you're talking to an electrician or a phycisist.

.
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Scriptural ramification: to him who has much, more will be given. And he who has not, even what little he has will be taken from him.

So, an overabundance of electrons attracts more electrons, stripping away all the electrons from the rest of the circuit?

Or, electrons balance themselves out, in a more orderly fashion?
 
Razeontherock said:
Scriptural ramification: to him who has much, more will be given. And he who has not, even what little he has will be taken from him.

So, an overabundance of electrons attracts more electrons, stripping away all the electrons from the rest of the circuit?

Or, electrons balance themselves out, in a more orderly fashion?
Click to expand...
Razeontherock said:
Scriptural ramification: to him who has much, more will be given. And he who has not, even what little he has will be taken from him.

So, an overabundance of electrons attracts more electrons, stripping away all the electrons from the rest of the circuit?

Or, electrons balance themselves out, in a more orderly fashion?
Click to expand...
Elements like to balence their last shells, not elements are comductors because of that .si,c,are semi conductors .they can be triggered ti conduct.
 
Razeontherock said:
Scriptural ramification: to him who has much, more will be given. And he who has not, even what little he has will be taken from him.

So, an overabundance of electrons attracts more electrons, stripping away all the electrons from the rest of the circuit?

Or, electrons balance themselves out, in a more orderly fashion?
Click to expand...
How do you mean? Electrical current is a tendency for electrons to flow from an area of high concentration to one of lower concentration, like most phenonmena in nature. In a circuit, electrons build up at the negative pole, and travel to the positive pole in order to "level out". Almost like water.
 
WIP said:
I didn't see anything but the flash at ground level. More like an impact.
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They're hiring dogs now lol.

Surveillance video released by the Apopka Police Department shows the bolt lighting up the parking lot Tuesday evening. A canine officer seen placing equipment in the backseat of his police SUV appears startled by the flash and hastily gets into the vehicle’s front seat.
 
WIP said:
I didn't see anything but the flash at ground level. More like an impact.
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Same here. My understanding is that the leader, which is actually a channel of lowered-resistance, ionized air, is not visible. Lightning that you can see is always upward moving. I'm sure there's exceptions to everything.
 
KevinK said:
How do you mean? Electrical current is a tendency for electrons to flow from an area of high concentration to one of lower concentration, like most phenonmena in nature. In a circuit, electrons build up at the negative pole, and travel to the positive pole in order to "level out". Almost like water.
Click to expand...

That doesn't jibe with what you said about the controversy over whether electricity flows from positive to negative
 
Edward said:
They're hiring dogs now lol.

Surveillance video released by the Apopka Police Department shows the bolt lighting up the parking lot Tuesday evening. A canine officer seen placing equipment in the backseat of his police SUV appears startled by the flash and hastily gets into the vehicle’s front seat.
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Yeah, I was looking in the car for the dog, too lol
 
Here's a diagram...

Conventional+current+Because+of+Franklin’s+work%2C+the+direction+of+electric+current+is+defined+as+going+from+positive+to+negative..jpg
 
Well think of how we were taught to test electrical on a car...+ to -

Is that not right now? It seems to work...
 
Edward said:
What about dc electric? If they taught me wrong, I want my money back lol.

Is lightning dc current?
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That diagram does depict direct current. It shows the conventional direction of flow (which is actually false), and the true direction of the electrons.

You'll have to take it up with Benjamin Franklin.
 
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