When you generate electricity where do the electrons come from? Is there some source of electrons like the conducting wire? What happens to them when they get to the motor or lamp.
I’m not sure where all the electrons are coming from or where they eventually end up.
They’re loosely bound to the metal atoms in the wires.
Electricity isn’t like water flowing through a pipe. With alternating current the electrons switch directions many times a second. They don’t really go anywhere. They just kind of jiggle back and forth where they are.
Think of the wire to the power plant as a long piece of rope running through many pulleys. The power plant gives its end of the rope a little tug and then lets it slip away many times a second. The rope doesn’t actually go anywhere, but you could hook a piece of machinery up to the other end of the rope and use those repeated little tugs to drive it.
Electrons certainly do flow. They can be stripped from one atom and move to another changing the net charge of each atom.
Wesley Clark,just having electrons is no big whoop but when you move them you have electric current. Don’t worry about your blender filing with electrons because current works in a circuit. It’s the electrons flowing through the motor that does work. Moving electrons through a conductor causes a magnetic field and vice versa.
In order to do anything with electricity you must have a circuit consisting of a complete loop from one terminal of the source out through various devices and back to the other terminal of the source. The source, like a battery, is the source of the electrons which leave the negative terminal of the source, go out through the loop and return to the positive terminal of the source.
We can’t say that the exact same electron that leaves the source travels all the way around the loop and returns to the source but on the average if 100 electrons leave the source negative terminal in some interval of time, 100 enter the source at the positive terminal in the same interval.
I read not long ago that a current density that corresponds to an average electron velocity (I think this is termed “drift velocity”) of a meter per second (walking speed) is about all you can get through ordinary wires without overheating them. So, a heavily loaded DC high tension transmission line used for very long distances has its electrons creeping along at much slower than a walk (to reduce heating losses they want to stay far below this limit), and an AC system at 50 or 60 Hz has its electrons shifting about the thickness of a few sheets of paper, in a repetitive cycle five or ten times too rapid to catch even if you could see them.
Of course there’d be a great variation in the electron velocities, with some individual electrons making quite a bit of headway.
Yes, but that’s not what Pochacco said. He said that electricity isn’t electrons flowing like water through a pipe, and that is certainly true. What you are talking about are chemical reactions, and at best tangentially related to electricity.
A great many electrical systems run on what is known as an earth return. Nothing returns to the other terminal of the source, it is simply bled away into the ground. There is no call for a circuit to return to the source to utilise electricity, it’s simply more convenient and sometimes more efficient to do so. But as anyone who has been struck by lightning would tell you, electricity can do plenty without ever going back to the source.
Not really.
As Napier points out electrons leave the negative terminal at an incredibly slow rate, at best at the speed of sound but in the vast majority of cases many orders of magnitude slower. Despite that electricity travels at a fair fraction of lightspeed, which is why international phone lines don’t have a 3 day delay.
So the source isn’t a source of electrons going out through the loop. Instead the source is a source of charge or current. You can think of the electrons in a wire as akin to the balls on Newton’s cradle (http://www.walter-fendt.de/ph11e/ncradle.htm ). When the source generates a charge it pushes one electron at approximately lightspeed, and that electron pushes an electron next to it and so on all along the wire. As a result the current is propagated at incredibly high speeds, while the electrons don’t actually move at all.
Of course all this is vital for earth return systems. If electrons really did go out through negative terminal then within minutes any earth return system would oxidise and crumble away into nothing because there is no direct return. Of course this doesn’t happen because the electrons get shunted without actually moving at al on average.
This is wrong. You are correct that there are earth-return circuits, but there is a return path to the other terminal of the source and it is the Earth itself. There must be a complete circuit path as David Simmons stated. He is, after all, an electrical engineer.
That’s a pretty spurious way of defining a return isn’t it? I pump electricty from Chile to Canada, and bleed it into the earth at the other end. Yet somehow the same current is said to be returning. It’s not returning in any real sense of course, it’s simply portrayed that way.
To illustrate this I could in theory rig up an earth return system fom the Earth to another planet. The generator/battery is located in Florida, the outlet on Mars and the earth plate in the martian soil. That will work just fine. But you can’t say that the current is returning to the generator via the earth despite several million miles of intervening vaccuum. vacuum. It’s portrayed as a return because any charge deficit is picked up by the planet earth itself.
Similarly many earth return systems have their earth plate located near ponds etc. in arid areas to give them the required conductivity in the soil. Yet the surrounding soil and bedrock are relatively non-conductive. Clearly the current isn’t actually returning via the earth, it’s simply balancing out on planet-wide scale.
Or we could set up a battery on an insulating mat and run the current through a light bulb and into the earth. There’s no way for the current to be returning in this case. Yet it will work just fine. If you don’t believe it touch the live wire of an electric fence while wearing no shoes and avoiding the positive wire. Current flows to earth and generates an electrical effect even without any possibility of returning to the source.
I take your point that the current is described as returning via the planet itself, but IMO that’s not a particulrly accurate description of what happens. The current doesn’t actually need to be able to return to the source for an electrical system to work, it just needs to be able to go to some other area with alower potential.
This is true but I think it’s a little misleading in the context of the question in the OP.
Yes, the electrons don’t need to return to the source for current to flow - for a while. And they only have to be able to go to some area of lower potential. However, the source is what maintains that potential difference so that they can continue to flow as long as the source maintains that potential difference.
It is certainly true that if there is a potential difference between two points electrons will move between them. The potential difference results from moving electrical charges around in an electric field, the potential being equal, in volts, to the work done in moving the charge. If the charges that were initially moved, or other identical charges, are allowed to move back to their original position the potential difference will become zero and the electrons will stop moving. There must be a return path to the source for the electrons, although not the same electrons, in order to maintain the potential difference.
I just now took a 1.5 v dry cell and my microammeter out in the back yard. I stuck the point of the negative probe in the ground and touched the positive probe to the positive terminal of the batter that I held in my hand. On the 200 microamp scale no current at all registered. When I then touched the negative probe to the negative terminal of the dry cell the meter exceeded it’s full scale reading on the 200 milliamp scale. From this I’m forced to conclude that with your proposed setup the bulb won’t light up although there might very well be a transient current through the light bulb to equalize any initial potential difference between the battery/bulb combination and ground. That, by the by, is equivalent to your lightning stroke which is certainly effective on a transient basis. However the lightning stroke is merely returning to the cloud electrical charges, electrons, that were carried away from it in the first place by raindrops or maybe dust particles.
The electric fences that I’m familiar with consist of a source with one terminal firmly attached to a metal stake driven into the ground and a single wire running from the other terminal of the source around whatever patch of ground you are trying to protect. There is thus a potential difference maintained between the wire and the ground and when I touch the fence allowing electrons to flow from wire to ground, or vice versa, an equal number flow between ground and the source so as to maintain the potential difference between the wire and the ground.
I agree with that in general. I was just trying to point out that the image of ellectrons physically flowing around a circuit from anode to cathode and back or vice versa isn’t particularly accurate IMO. Electrons are shunted from or towards the ‘source’ but there isn’t any literal flow in the sense than an electron from Europe literally arrives at my phone speaker when I make an inetrcontinental call. The electrons that started at Europe stay in Europe insofar as individual elctrons can actually be traced. The current flows, the electrons stay at home.
The reason I introduced Earth returns is that it shows that up quite well. If electrons literally flowed then their would be all sorts of problems. But so long as the electrons simply get shunted it’s not an issue. It just seems like speaking of eelctrons being pressurised would be more accurate than sayingt hat the flow.
I never meant to suggest that a normal penlight battery would suffice for a simple earth effect like that. But certainly if the potentially were great enough current will flow without a complete circuit, transient though that may be. Perhaps a capacitor might have been a better bet.
That’s why I wrote in my first post:
I don’t see that you and I have any real disagreement.
I disagree. 
Perhaps I should have been more clear in my answer. The water analogy isn’t a good one as it can be easily misunderstood but it can be correctly applied as a model for a loop circuit through a pipe or flowing from high potential to low potential in a different place such as a dam and generator. The basic misunderstanding is that the water doesn’t have to flow completely through the circuit to do work, it just has to move.
Wesley,
Read this: http://amasci.com/ele-edu.html and come back with another round of questions.
The electricity as a whole does flow back though. The electrons that go into the earth may flow a few feet, which push the electrons in front of them a few feet, which push other electrons, etc. The water metaphor is a good comparison here. If we pump water through a pipe from the North American Atlantic coast to the European Mediterranean coast, it’s safe to say those molecules of water won’t return within millions of years, but the entire ocean does flow our way just slightly and we never run out of water. On the other hand, pump that water to Mars and - even if it takes millions of years - we will run out eventually. Our planet is a huge capacitor for both electrons and water molecules, but start pumping them to another planet and they’ll never come back (unless you start pumping the other direction).
I like to think of electricity in a wire as being represented by a long narrow tube stuffed full with table-tennis balls. Put a ball in at one end, and after only a short delay a ball drops out of the other end. It’s not the same ball, but it might as well be, as they’re all identical anyway.
The actual speed of electrons in a wire is about walking speed - pretty slow, but give them a break, they’ve only got tiny legs.
You can get apparent electron flow without any actual transmission of electrons. No actual electrons flow through (ideal) capacitors or vacuum tubes/valves. And though it is true to say you don’t need a return path for electrons to flow, just a difference in potential, it must be noted that you need some sort of ultimate reference in order to measure the potential in the first place. For us, the ultimate reference is the planet, and you can think of the electrical model of earth as a whole shitload of paralleled resistors, so the planet as a whole is a rather good conductor. The return path from your domestic power supply to the power station is the earth itself - the neutral terminal of your house should be near earth potential, and the neutral terminal of the power station is seriously earthed. It saves 50% on transmission cables using earth returns, but I’ve always wondered whether it tingles earthworms near the electricity substations.
IIRC, earth-return signalling was used for communications between the trenches during WW1, without any wires between transmitter and receiver.
I’ve designed air ionisers in the past, and all they do is spurt out electrons by means of a high negative voltage on a pointy conductor (charge tends to congregate on a point). This voltage is, of course, referenced to earth. The electrons don’t float about freely in the air, but hitch a ride on air molecules by ionising them. These negatively charged air ions drift towards surfaces with a more positive potential, but it’s not their destiny to do so. They’re repelled from the pointed emitter, and this creates a small ion wind, though where it ultimately blows is of no consequence.
First, the water flow model for electricity isn’t bad. If you don’t mind substituting hydraulic fluid for water, you can picture your hydraulic brakes on your car. When you tromp on the pedal, fluid moves through the tubing, but it doesn’t go very far. Its action travels instantly (as far as you could tell) because as soon as you push on the pedal, brake parts at the other end move. But if you put dye in at one end, it’d take a very long time before you start noticing color at the other end. A great example for alternating current would be if you shout in a hallway - someone hundreds of feet away hears you in something like a second, but it’d take years for your bad breath to bother them.
And, second, I don’t think you can start with everyday observations and reason your way to concluding that the individual electrons don’t travel very fast or very far. Seems to me it’s a pretty obscure thing, calculating how fast the electrons themselves move. I think if I had to do it, I’d use special relativity and, more specifically, the Einstein - Lorentz contraction, starting with how strong a magnetic field a coil produces and working my way back to how many electrons had to move how fast to do that.
Who has an easier way than that to calculate how fast electrons move when a current flows?
I’m impressed you know any way to calculate electron speed in a conductor. For very high speed work I’d need to know the speed of electricity in a particular conductor*, but I’d just look it up, or rely on one much fonder of maths than I to write simulation software that I can use.
As alternating current makes obvious, electrons do not actually have flow from the source to the load in order to transport energy. In fact the energy in an electrical circuit propagates via an external electromagnetic wave, and the conductor and its free electrons only act as a guide for this wave.
It seems we have covered the “what happens to them” end of it pretty well but Pochacco’s “loosely bound to the metal in the wires” is the only answer so far to the first question.
That answer is a good one. For the electricity that we use in homes and elsewhere, the electrons are in the materials of the source, the “motor or lamp,” and the wires that connect them to the source.
In the strict sense we don’t “generate electricity.” The electricity is already there in the form of the protons and electrons. The process referred to as “generating electricity” is really one of doing things that make the charged particles move. And those that move the easiest in solid conductors are the electrons. So what happens is that a potential difference is created by some mechanical or chemical means and that potential difference causes the movement of electrons in the materials of the various components of the system.
To go a step further. The movement of the charges in a resistive material like the filament of a lamp results in the production of heat that raises the temperature of the filament to the point were it glows and produced light. The moving charges in a motor produce magnetic fields that interact in the motor so as to make its rotor turn. In addition, if we vary the potential difference as time passes the moving charges change velocity, or accelerate. An accelerating charge produces electromagnetic waves that travel away from the accelerating charge at the speed of light giving us radio and TV.
And I hope Wesley Clark is still around.