It is part of the path, or a potential one at least. The reason it exists is a outlet has 3 wires, neutral and ground being similar potentials. If there is a short inside a piece of equipment where the hot (dangerous) wire touches the case a breaker or fuse blows, removing the threat.

The ground wire on an outlet never, ever carries current. This allows for GFI plugs in the bathroom, where there is a lot of water connected to metal plumbing that is througly grounded. If it senses any current in ground it trips.

Sorry, I'm not sure if you're replying to mine or another's post...

 

"Consuming all the voltage" - I'm not sure what that means. Is that mentioned in the book before this chapter?

I'm not familiar with terminology like "common side" of this and that, but I think what you mean is, I can hang from a wire from my hands and feet and not get a shock, but I can't hang from a wire on one side of a component and have my feet hanging from another wire on the other side of the component.

What I can hear someone having trouble with is that while there is no voltage between the point where they're grabbing the wire with hand and the point where they've reached up with a foot to hang from the same wire, but a few feet further along that same wire, are we still not between the neg. terminal and the pos. terminal, between that voltage?


Many thanks.

Always keep in mind that electric current will always follow the path of least resistance (MORE) readily, than a path with a higher resistance.

So if you had a strraight wire with a certain resistance, current will flow through it readily, but if your horse shoe shaped object would have lesser resistance than the wire than PART of that total current flowing would branch off through that object as well.

Current flow is the inverse proportion to the amount of resistance it flows through.

So if your touching the positive side of the load and you are connected to the neg. (ground, common) side of that load current will branch off in inverse proportion to the amount of resistance you are appearing to be ACROSS that load.

If you touch the wire on the neg side of the load and you were touching the neg. (common, ground) a few feet away, than if you were presenting a lower resistance than the wire between your hands and feet, you will receive PART of the total current, with respect to the resistance you present across the wire your in parrallel with.

More than likely a wire will always have less resistance than your body, so most if not all current will flow through the wire to ground.

So always remember any time you touch a straight wire at 2 points you present a resistive current path in parrallel with the distance of the wire between your 2 points of contact.

So your safe to touch a straight wire at 2 points, OR ARE YOU?

What happens if the wire between the 2 points off contact your making begins to increase in resistance it's a straight piece of wire, so how can it be harmful, well if the wire BETWEEN the 2 points of contact your making, begins to increase in resistance due to failure, and the resistance begins to approach the resistance of your body now current will be forced to take another path in inverse proportion to the amount of resistance you and that length of wire is presenting at that point in the circuit.

Which is what you don't want to happen. Thats why appliances are grounded, so if the appliance comes in contact with the high potential (resp. to ground), than the appliance itself becomes a path to ground so you don't take the full load yourself.

Hope this helps out too.

 

The problem. as I see it, is the picture shows a battery. If the source is AC voltage, then yes the OP is correct in their assumption stray voltages would shock the character.
However, the real concern is not whether it is AC or DC, it is the insulation. I do not know where you all live, but all the wires here in Houston, (and most places I've lived), are insulated. If a bird landed on non- insulated wires, having two feet, they would be shocked. AC, or DC.
Dan

 

The problem. as I see it, is the picture shows a battery. If the source is AC voltage, then yes the OP is correct in their assumption stray voltages would shock the character.
However, the real concern is not whether it is AC or DC, it is the insulation. I do not know where you all live, but all the wires here in Houston, (and most places I've lived), are insulated. If a bird landed on non- insulated wires, having two feet, they would be shocked. AC, or DC.
Dan

I don't think so. Here is a quote from a Bird Impact Assessment Study on a 400kV line.
The voltage gradient between a bird's two feet is negligible.

 

Hey Ron,
Yes, but the bird still conducts. Because they do not die from the electrical charge, there is no reason to show any correlation between a human touching the hot wire to ground without showing how the same would happen to the bird. Using the bird and the human to show how grounding works confuses the point.
That is the original question. Why not go ahead and fry the bird?
Dan

 

Hey Ron,
Yes, but the bird still conducts.

To what?

With such high-voltage, high-power lines, the wires are so far apart that they can't possibly contact more than one at a time.

Because they do not die from the electrical charge, there is no reason to show any correlation between a human touching the hot wire to ground without showing how the same would happen to the bird.

Humans are much larger than birds that can fly.

Using the bird and the human to show how grounding works confuses the point.
That is the original question. Why not go ahead and fry the bird?

Because the bird's body isn't large enough to short between a pair of live wires, or a live wire and ground.

If a bird simply lands upon a high-voltage wire, even uninsulated, they will be perfectly safe - as long as they are not large enough to touch another wire energized to a different potential, or ground.

 

Hey Sarge,
Look at the representation the OP is asking about. It is confusing at best.
And when does a parallel circuit not conduct? The bird does conduct, just not enough to be affected. The picture is okay if you understand grounding in the first place.
Also, if I haven't siad it before, You are one of the best.
Dan

 

Hey Sarge,
Look at the representation the OP is asking about. It is confusing at best.
And when does a parallel circuit not conduct? The bird does conduct, just not enough to be affected. The picture is okay if you understand grounding in the first place.
Dan

THANK YOU!

 

Hey Winston,
You are welcome. What Sarge wrote about potential is correct. Here is the problem: no representation looks right. Yes, it does look like the bird should be shocked, but it is not connected between two ends.
Of course I am not explaing this as well as a teacher, but then again, I am the handyman
Dan

 

Hey Winston,
You are welcome. What Sarge wrote about potential is correct. Here is the problem: no representation looks right. Yes, it does look like the bird should be shocked, but it is not connected between two ends.
Of course I am not explaing this as well as a teacher, but then again, I am the handyman
Dan

The bird? Wait... I never mentioned the bird. The bird looks like it should be shocked? I didn't think so. I don't see a return path for the bird. Always seemed reasonable to me that without a return path, there's no circuit, and no current. Forget about the bird.

There is a guy (not a bird) in the diagram, on the bottom side of the resistor. There is, in that diagram, a PATH from the wire, through the guy, through the ground and up the grounding rod. A path. A return path. A circuit.

Just saying, "they're all electrically common" doesn't explain what is going on to someone who is only at that point in the book. Don't you think? The man is between the terminals of the voltage source. Voltage is like gravity in that it is potential that gets less and less as you get nearer the ground. How does one reconcile that with "zero drop between electrically common points"?

Another poster said, "the resistor consumes the voltage"... Really. Someone who has read just that far in the book understand what you mean by "consumes the voltage"? Really? There is a mouth in the resistor, and it's eating the voltage for dinner...

 

The bird? Wait... I never mentioned the bird. The bird looks like it should be shocked? I didn't think so. I don't see a return path for the bird. Always seemed reasonable to me that without a return path, there's no circuit, and no current. Forget about the bird.

There is a guy (not a bird) in the diagram, on the bottom side of the resistor. There is, in that diagram, a PATH from the wire, through the guy, through the ground and up the grounding rod. A path. A return path. A circuit.

Just saying, "they're all electrically common" doesn't explain what is going on to someone who is only at that point in the book. Don't you think? The man is between the terminals of the voltage source. Voltage is like gravity in that it is potential that gets less and less as you get nearer the ground. How does one reconcile that with "zero drop between electrically common points"?

Another poster said, "the resistor consumes the voltage"... Really. Someone who has read just that far in the book understand what you mean by "consumes the voltage"? Really? There is a mouth in the resistor, and it's eating the voltage for dinner...

Winston, were you perhaps badly shocked when you were an infant?

Lefty

 

Winston, were you perhaps badly shocked when you were an infant?

Lefty

Very internet.

 

I guess, for some reason, something is happening with that one component such that being on one or the other side of it means something, but it doesn't say what. There is still a voltage on one side of you, and the ground leading to the grounding rod to the zero potential terminal on the other side of you.

I get that "electrically common" means the wire could be there, or it could be shorter, or the component could be directly on the terminals. But I can't get from there to seeing why being on one side of a component matters. Am I not still between one side of the source and the other? Many thanks.

Did you go through Chapters 1 and 2 before diving into 3?

Still, it must be the case that there is such a thing as a safe side of a circuit, otherwise why have this chapter at all?

No. There is no guarantee whatsoever of any intrinsically safe part of a circuit. The section in question on electrical safety is intended to illustrate that there are parts of a circuit which are more dangerous than others.

Yes, but the bird still conducts. Because they do not die from the electrical charge, there is no reason to show any correlation between a human touching the hot wire to ground without showing how the same would happen to the bird.

The resistance of the wire is negligible compared to the resistance of the bird or the human. Per Ohm's Law, current through the bird or human will be negligible. This is why linemen can work hanging from uninsulated lines once their helicopter has come to the same potential. http://www.youtube.com/watch?v=9tzga6qAaBA&feature=related Birds are unable to touch both the hot wire and ground at the same time. Humans, much to our peril, can.

Just saying, "they're all electrically common" doesn't explain what is going on to someone who is only at that point in the book.

Did you go through chapters one and two before diving into three? If so, please re-read this: http://www.allaboutcircuits.com/vol_1/chpt_2/7.html If not, please try here: http://www.allaboutcircuits.com/vol_1/index.html

 

Did you go through Chapters 1 and 2 before diving into 3?

No. There is no guarantee whatsoever of any intrinsically safe part of a circuit. The section in question on electrical safety is intended to illustrate that there are parts of a circuit which are more dangerous than others.

The resistance of the wire is negligible compared to the resistance of the bird or the human. Per Ohm's Law, current through the bird or human will be negligible. This is why linemen can work hanging from uninsulated lines once their helicopter has come to the same potential. http://www.youtube.com/watch?v=9tzga6qAaBA&feature=related Birds are unable to touch both the hot wire and ground at the same time. Humans, much to our peril, can.

Did you go through chapters one and two before diving into three? If so, please re-read this: http://www.allaboutcircuits.com/vol_1/chpt_2/7.html If not, please try here: http://www.allaboutcircuits.com/vol_1/index.html

By "just saying they're electrically common..." I didn't mean to imply that I'd not read about the particular concept of being electrically common. I wasn't saying, "hey, what does electrically common mean, anyway?" But I can see that one could think that by the way I worded it...

I'm trying to see why there isn't a current going through the guy/ground/grounding rod/return terminal. How is the potential at the mans hand the same as the earth? How is it that those two points are electrically common?

It occurred to me to imagine that if that copter in the vid had a wire going from the line to it, then there wouldn't be an imbalance between it and the line and the guy wouldn't get a current through him from undischarged static or whatever. I suppose then that a line from the wire to the earth means there's no imbalance, so there's none between that wire where the man's grabbing it and the earth, either. Is that closer to it?


"Contrary to popular wisdom, seeing is not believing. Seeing is where belief ends because it is no longer needed." -Terry Pratchett 'Pyramids'

 

Hang about...

 

It's good to finally understand this. To those who were helpful, many thanks. And to think I didn't have to pay thousands of dollars to find out... And I'll be able to turn around and tell others for free.

 

Hey Winston,
You ain't giving that info out for free. No how no way.
But seriously, folks. Your time and knowledge is earned. So you already paid. Give knowledge to those that accept learning.
Dan