electrons: whimpy vs. powerful

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  #1  
Old 01-24-06, 10:45 AM
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electrons: whimpy vs. powerful

I need a book on the "nature" of electricity. Guess I'll be heading for the library, for months of reading. But for now, I'll ask some more questions here.
I turn on a light. Powerful electrons race through a conductor to the element, light the bulb, then return to the POCO as whimpy electrons, right?
That's the nature of electicity, more or less, correct? It seeks the path of least resistance, on it's return from the light bulb. So instead of going through the ground wire at the main panel, into the ground rod (water pipe or whatever), it races through the neutral wire, back home to the POCO.
Okay, what happens when a hot wire comes loose from its terminal in an outlet box, touches the metal box, then, races back to the main panel. Since this current is not whimpy, does it go to the ground rod, into the Earth, instead of seeking the path back to it's source, at the POCO? Or, does this powerful electricy also go back through the neutral conductor, back to the POCO? This is one of the many aspects of the nature of electicity that confuses me.
 
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Old 01-24-06, 11:06 AM
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Originally Posted by Willg54
It seeks the path of least resistance, on it's return from the light bulb. So instead of going through the ground wire at the main panel, into the ground rod (water pipe or whatever), it races through the neutral wire, back home to the POCO.
This is a common misconception. Electricity take ALL available paths. The amount of current through each path is inversely proportional to the resistance of the path.


Originally Posted by Willg54
Okay, what happens when a hot wire comes loose from its terminal in an outlet box, touches the metal box, then, races back to the main panel. Since this current is not whimpy, does it go to the ground rod, into the Earth, instead of seeking the path back to it's source, at the POCO? Or, does this powerful electricy also go back through the neutral conductor, back to the POCO?
This case is no different than the normal case, where a load is present. However, the electricity has no resistance so more current flows than the wires can handle. The circuit breaker detects the over current, and trips (or the fuse blows).
 
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Old 01-24-06, 11:32 AM
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racraft, "my bad", as they say. Of course, the breaker would trip. I wasn't thinkin' straight. However, wouldn't SOME electicity travel through the ground wire, back to the main panel. After all, isn't that what the ground wire is there for, to catch SOME of the electricity that "escapes" into the system, BEFORE the breaker trips?
But, just for curiosity's sake, what if you were to supply 120 volts to the ground wire in an outlet, 120 volts coming from a source with no breaker, and the current was allowed to run back to the main panel. Would the powerful electrons proportionally disipate, dividing themselves between the neutral path, back to the source, and the ground path, to Earth? And if so, I'm assuming there is more resistance to the ground path, thus, more would go back to the source. If 120 volts of strong electricity were allowed to return to the source, would this damage the transformer at the pole, for example.
If this question makes no sense, then sorry again, for my ignorance. I was just curious? Just tryin' to make sense of all this stuff.
 
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Old 01-24-06, 01:00 PM
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The e-books should help you.
Start with Volume 1 DC, chapter 1&3


Down load the E-book's pdf files
http://www.ibiblio.org/obp/electricCircuits/index.htm

The books are large so it will take time to down load.
 
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Old 01-24-06, 04:17 PM
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I believe you are operating under a misconception. The same current flows in both wires of the circuit. It is the potential of the circuit that is different on either side of the light/motor/object using electricity. The neutral side is at or close to ground potential (more on this later) while the hot at 120vac. What makes electrons flow is the difference in potential between two electrically connected points. The amount of current depends on the resistance of the circuit between those two points - the less resistance the more current. The current does work whether it is making light, heat, making something move or a combination of all those. The thing to note is that the electrons do not get used up, weaken, or leave the circuit in any way. They just change potential.

I mentioned earlier that the neutral may be close to but not at ground because the wire in the circuit has resistance and the current flowing in the neutral wire will result in a slight potential relative to ground. The more current the greater the potential difference. As to where the electrons go on the neutral side they will take the path of least resistance. Since the neutral wire to the pole is much larger than your ground wire most of the electrons will flow there (larger wire = less resistance).

Even the earth can have a local charge based on the amount of electricity flowing into it. During a lightning strike the potental of the earth can rise dramatically in the immediate area while the electrons dissipate into the earth. At that point electrons could flow up the ground wire and into the neutral to the pole or into the house.

Hope this helps. And keep asking questions.

Steve
 
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Old 01-24-06, 08:07 PM
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WOW, Bob, the plot thickens. It's all coming together, slowly, but each time I get more information, I can better make sense of all this stuff. So, thanks for sharing your knowledge. Maybe one day(in my next life time)I will be able to explain this stuff to some other inquisitive person. I'm gonna do some reading, and maybe the picture will clear a bit. Until then, get ready for more questions!
 
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Old 01-24-06, 08:12 PM
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Electrons are electrons. For purposes of this discussion, they do not change energy as they travel. The current flow is a measure of how MANY electrons are flowing, and the voltages around the loop change as the current passes through various series and parallel paths to reach the other side of the source.


Now, if you are not confused yet, consider hole flow, which is the movement of positive charges in the opposite directions as the electrons. That should give you some late night reading!
 
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Old 01-24-06, 08:55 PM
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mmmm?!? Fewer electrons on the neutral side of, ie., a light, means less voltage, right? Like, how MUCH less voltage, give or take? So, are there fewer electrons because some of them were used up, (or converted might be the more correct term), as they were being turned into light, heat, or motion?
Is that ANYWHERE NEAR the right assumption?
 
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Old 01-25-06, 09:13 AM
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NO undefined
A difference in potential electromotiv force ( voltage ) causes current ( electrons) to flow. The current ( # of electrons ) is the same at every point in the circuit. When current flows through a material which resists current flow, heat is given off by the material proportional to the square of the current. Electric wires have very low resistance, so very little heat is given off. A device like a light bulb has an amount of resistance, so heat is given off. The nature of the filament material ( tungsten) is such that when heated, it also emits light. How convenient!

As far as the actual electron travel, what actually is going on is that one atom with an excess charge bumps the next atom which bumps the next one, etc. etc. You will need to talk to someone with much better theoretical grasp than me to find out where all these electrons really are!

When we get to motors, that is a whole different concept, because now we get into the interaction between and alternating electric field with a magnetic field. Film at 11.
 
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Old 01-25-06, 10:45 AM
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You've asked a question that really requires several hours of discussion to make clear. The best that you can hope for here is a couple of approximations, and you will really need to find a good physics text to add the necessary pictures and concepts.

You first need to understand the concept of 'potential energy'. Potential energy is that energy 'stored' by the _position_ of an object as a result of the various forces acting on the object. You are probably most familiar with gravitational potential energy. A rock 100 feet in the air has a certain amount of energy stored, not in the rock itself, but in the relative position of the rock and the Earth. If you simply drop the rock, it will accelerate, with the potential energy being converted into kinetic energy. The rock itself remains unchanged(we are ignoring relativistic physics for now), but the potential energy associated with the rock is being converted into kinetic energy associated with the rock. Depending upon how you are doing the accounting and using terminology, it is fair to say that the rock is losing potential energy and gaining kinetic energy, but that the rest energy of the rock remains unchanged. When the rock hits the ground, the kinetic energy will get dissipated all over the place, and become thermal energy.

If we were to instead arrange a system whereby the falling rock did something useful (say by lifting up some water for irrigation), then we could convert the potential energy of the rock into some other form of energy useful to us. Note that there is a natural direction of flow: rocks fall down, but we have to intentionally pick them up. Objects tend to move from locations of higher potential energy to regions of lower potential energy, doing work along the way. To move an object from a region of low potential energy to a region of high potential energy requires the input of external work.

Electrons similarly have potential energy, which depends upon the _location_ of the electron and the forces acting upon it. When an electron moves from a region where it has higher potential energy to a region where it has lower potential energy, it can do work.

The conductors feeding your home are maintained in a state of being at different potential energy levels for the electrons that they contain. We'll neglect for a moment just how this is done. When an electron is moved from higher potential to lower potential, it does work. This work might be in the form of picking up a bit of speed and then transferring kinetic energy to the bulk material (resistance heating), or it might be in the form of interacting with a magnetic field, causing the conductor to move (electric motors), or it might be some other event. But the point is that an electron has moved from a region of high potential to a region of low potential, doing work in the process. The electron itself remains totally unchanged; simply its position relative to external forces has changed.

Now, when the electron moves from a region of high potential to a region of low potential, something interesting happens. The electron is itself a source of electrical forces, and it acts on all the other charged particles around. When the electron moves from high to low potential, the forces that create the regions of high and low potential much change thereby. The high potential gets a bit lower, and the low potential gets a bit high. If you let enough electrons move, then the two potentials would become equal, and then no further work could be extracted from permitting electrons to move.

So the power company must continually supply electrons in the high potential region, and continually collect electrons from the low potential region, and must continually 'pump' the electrons from low to high potential. So in this sense the electrons are changing condition; but the condition is based solely on the _location_ of the electrons, and not in any aspect of the electrons themselves.

-Jon
 
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Old 01-25-06, 02:37 PM
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Originally Posted by Willg54
Okay, what happens when a hot wire comes loose from its terminal in an outlet box, touches the metal box, then, races back to the main panel. Since this current is not whimpy, does it go to the ground rod, into the Earth, instead of seeking the path back to it's source, at the POCO? Or, does this powerful electricy also go back through the neutral conductor, back to the POCO? This is one of the many aspects of the nature of electicity that confuses me.
In typical electical service installations, the return conductor and the earth grounding conductors are "bonded" together.
Depending on the situation, a fault that causes current on the grounding conductor should trip a cicruit breaker, or a GFCI.
 
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Old 01-25-06, 02:52 PM
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Originally Posted by Willg54
racraft, "my bad", as they say. Of course, the breaker would trip. I wasn't thinkin' straight. However, wouldn't SOME electicity travel through the ground wire, back to the main panel. After all, isn't that what the ground wire is there for, to catch SOME of the electricity that "escapes" into the system, BEFORE the breaker trips?
The purpose of the ground wire is to cause electrical current to pass back to the panel earth point (bonded to supply neutral so it can flow there), to keep the current from flowing through any person or animal.
But, just for curiosity's sake, what if you were to supply 120 volts to the ground wire in an outlet, 120 volts coming from a source with no breaker, and the current was allowed to run back to the main panel. Would the powerful electrons proportionally disipate, dividing themselves between the neutral path, back to the source, and the ground path, to Earth?
They would try and dissipate as much as the wire will let them. Usually as heat, and depending on the properties of the conductor, too much heat, hence the need for a curcuit breaker, to open before the wire dissipates more heat than it should.
And if so, I'm assuming there is more resistance to the ground path, thus, more would go back to the source.
Learn Ohms law. An increase of resistance (R), would reduce the amount of electrons that flow, and cause them to dissipate as heat.
If 120 volts of strong electricity were allowed to return to the source, would this damage the transformer at the pole, for example.
It would damage or work the point of greatest resistance.
Be it a light bulb filament, heater element, motor winding,
branch wiring, fuse/breaker wiring, meter, service drop, transformer primary fuse, maybe the trasnformer or uven the substation, if it is that stretched.
 
  #13  
Old 01-25-06, 04:09 PM
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The way I learned it in physics, which may be too simplistic to be helpful, is with water analogies.

If you open a supply pipe in your house, it's under pressure and you get a lot of water in a short amount of time. The amount of water depends on the pressure and the size of the pipe. You can use this pressure and volume to do work, for example rotating a sprinkler. That's the ungrounded 'HOT' conductor.

If you open a sewer pipe, for example a cleanout on a horizontal pipe, nothing happens because the water is just flowing by gravity and is not under pressure. If you could see electrons flowing, you would see the same thing. That's the grounded 'neutral' conductor.

Voltage = psi, Amperage = pipe diameter.

If you want a medium that is more comparable in terms of lethality, steam would be good. The supply can kill but you could drink the condensate in the return line.
 
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Old 01-25-06, 04:19 PM
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Similarly, I learned physics very simplisticly. I turn on a light switch, the light comes on, and I am happy. I can, therefore, devote more time to practical matters. Y'all have fun!!!
 
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Old 01-26-06, 01:14 AM
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Exclamation

Originally Posted by ArgMeMatey
If you open a sewer pipe, for example a cleanout on a horizontal pipe, nothing happens because the water is just flowing by gravity and is not under pressure. If you could see electrons flowing, you would see the same thing. That's the grounded 'neutral' conductor.
No such luck.

The neutral (grounded conductor) has the exact same pressure as the hot (ungrounded conductor).


Cut a neutral while the light is on, get in the middle, and you are dead.
Check it with a volt meter and you have 120V just the same.
It falls near 0V only because it is connected through to the drain.
Unhook it an the full pressure is there.
 
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Old 01-26-06, 05:41 AM
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If you want a water pipe analogy (which is only a very rough analogy), think of the neutral as a return pipe in some sort of closed loop heating system.

At the source, you have a pump. It draws hot water from some sort of open cistern, and pushes it into a pipe. Because of the pump, the water entering the pipe is under high pressure.

As the water flows along the pipe, because of friction, the pressure drops a bit. If there is a valve anywhere in the system, and the flow gets stopped, then the pressure upstream of the stoppage becomes high and the pressure downstream drops to zero.

Then you get to the actual heating unit. The heating unit has lots of small tubes and fins and such to carry heat from the water to the air, and there is quite a bit of friction here. On the exit from the heating unit, the water pressure has dropped considerably because of the flow, but the water is still under pressure. Now the water flows through the return pipe to the open cistern. At the open cistern, the pressure is _zero_.

Now, if you _plug_ the pipe anywhere, even _after_ the load, then the flow stops. Because there is no flow, there is no friction loss, and the pressure rises to the full value.

-Jon
 
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Old 01-26-06, 08:13 AM
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Originally Posted by bolide
No such luck.

The neutral (grounded conductor) has the exact same pressure as the hot (ungrounded conductor).


Cut a neutral while the light is on, get in the middle, and you are dead.
Check it with a volt meter and you have 120V just the same.
It falls near 0V only because it is connected through to the drain.
Unhook it an the full pressure is there.
You're right, of course, but that is not what I said. I said open a cleanout on a horizontal pipe, not "cut the pipe." Is it accurate to say that using the electrons to do work slows them down? I think the situation Winnie mentioned subsequent to your post illustrates what you're talking about.
 
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Old 01-26-06, 08:21 AM
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Thumbs up

Originally Posted by winnie
If you want a water pipe analogy (which is only a very rough analogy), think of the neutral as a return pipe in some sort of closed loop heating system.
Excellent, Jon!
 
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Old 01-26-06, 09:36 AM
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Originally Posted by ArgMeMatey
I said open a cleanout on a horizontal pipe, not "cut the pipe."
Looking at Jon's analogy, you tee into the downstream pipe.
Take the plug out and water squirts out.



Is it accurate to say that using the electrons to do work slows them down?
They always travel at the same speed in copper at a given temperature irrespective of voltage or amperage.



You can think of the resistance provided by the load as some skinny piece of pipe.
A night light is a long capillary tube.
A light bulb is 150' of 1/4" tubing.
A blow dryer is 10' of 1/4" tubing.

All this does is limit the maximum flow in the system.

Of course, no analogy is perfect. And this one fails if you consider heat extracted from the system. Because clearly the blow dryer extracts more energy from a circuit than does a light bulb.

Resistance is inversely proportional to power.
So Ohm's law doesn't work for a hydronic heating system.
 
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Old 01-26-06, 10:31 AM
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Let's discuss a "central" vacuum-cleaning system.

Vacuum-lines, in the form of pipes, "connect" the vacuum-producing motor to "inlets" at convenient locations.

First, You start the motor---next, you lift open the seal-plate on an 'Inlet", and there is immediately a "current" of air flowing into the inlet and thru the vacuum-line.The air-flow will continue as long as the vacuum-motor is operating.

What is the physical force that causes the air-flow?
 
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Old 01-26-06, 10:50 AM
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Originally Posted by PATTBAA
What is the physical force that causes the air-flow?
Gravity.

Sounds silly. But you are basically undermining the air on the inlet side of the motor. So air above the inlet falls and pushes air toward the motor.
 
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