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Probably worth asking the OP whether he's passed through understanding and into a world of
infinitequantum darkness about now.
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Charge (or current depending on your pedantry) does not flow as electrons, it's flows as EM fields between electrons.
This is bullshit (or bollocks, depending on which side of the Atlantic you reside).QuoteHowever this means the classic text book battery being a chemical reaction that moves electrons through a membrane creating positive and negative ions and then returns them via the circuit has to be wrong as the electrons cannot traverse the circuit fast enough.
Classic textbooks are generally classic because they are correct. It seems a bit of a stretch to call them wrong.
For a simple analogy, think of a long tube completely filled with marbles. If you push a marble in at one end, a marble pops (immediately) out the other end. But is it the same marble? Does it have to be the same marble for marbles to have flowed along the tube?
If your tube is 10 metres long and you push a marble in one end and a marble pops immediately out the other end, how fast did the marbles travel along the tube? Did they travel at more than 10 metres per second to get from one end to the other, or was it rather slower than that?
There is perhaps a "marble field" that prevents marbles getting bunched up together in the middle of the tube and forces them to stay one marble apart from each other. -
The marble idea does not cut it. It's basically saying in "Newtons balls" the middle balls do not move, but the mommentum transfers instantly (at the speed of sound in the balls). However, that works for 1 marble/swing. If you want to put 1,000,000 balls _through_ the device then the middle balls must move at the speed of the overall flow.
Why your brain thinks this does not cut it is because it's the wrong analogy but it's nevertheless close to the truth. The error is in making the analogy flow along a pipe as if that's driven by hitting things. It's not applying momentum to a particle, it's the space the particle takes up in the pipe which in the physical analogy increases the pressure at the start of the pipe, leading to pressure drop along the pipe which leads to flow (i.e it's all really about charge, potential, potential differences with their concomitant electric fields and current).
Obviously in practice the electrons don't form orderly ranks and march forward down a conductive 'pipe', in fact they follow a random path charging around at their Fermi velocity (fractional light speed) with an overall physical drift along the pipe at their drift velocity which is considerably lower and is determined by the electric field they are subjected to. It is the electric field that propagates at some fraction of the speed of light and causes electrons at the end of the 'pipe' to dribble out. The electric field is in volts/m and the relationship between that and electron drift velocity explains why when you apply a certain voltage across a (resistive) conductor you see a characteristic current pass along the conductor which if you want a hard time you can calculate from the drift velocity equations or you can opt for the simpler Ohm's law.
For a moment forget that it is the electric field driving this, there is still an underlying classical physical phenomenon taking place. When the current leaves the wire electrons do physically leave the wire. If you doubt this, connect that wire to an electron driven cathode ray tube and you can see the effects of electrons flying through vacuum and hitting a phosphor screen. If electrons are leaving the wire the charge on the wire must be becoming more positive. That positive charge on the wire drags more electrons into the wire.
It's also that movement of charge that generates the potential difference, that generates the electric field, that moves the charge, that generates the potential difference... You can see where this is going. For more details see Professor Maxwell, this daemon will lead you to him...
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Probably worth asking the OP whether he's passed through understanding and into a world of
infinitequantum darkness about now.
I'd put money on it. -
Electricity is about the valence electrons. When a valence electrons shift from one atom to the next this is your current . When a valence electron is pulled from it's highest orbit the atom it becomes a free electron until it latches on to another more positively charged atom .When the speed of the valence electrons moving from atom to atom increases the current increases. In the case of earth grounded battery it more about potential energy. Electrons will move from the highest to the lowest potential . Even when the potentials are of the same charge .Since air and earth is not a perfect insulators it would still act as a full circuit from the negative to positive. But the transfer of valence electrons would be very very slow across the different potentials . So the current would be nearly in-detectable .
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When a valence electrons shift from one atom to the next this is your current . When a valence electron is pulled from it's highest orbit the atom it becomes a free electron until it latches on to another more positively charged atom .When the speed of the valence electrons moving from atom to atom increases the current increases.
Not really. Valence electrons are relatively firmly attached to the atoms, they don't move about (except minimally back and forth between the adjacent covalently bonded atoms that share them*). In a conductor, when a valence electron gets enough energy it becomes a conductance electron and conductance electrons move about in a conductor pretty much like atoms in a gas, baring occasional, relatively rare, recombinations with atoms they don't move from the valence band of one atom to the valence band of the next and so on. Instead what you get is an 'electron gas' of conductance electrons forming in the conductor. What makes the difference between a non-conductor, a semi-conductor and a full blown conductor is how much energy is required to promote an electron from the valence band to the conduction band - the less energy required for this promotion, the more conductive a material is (simplistically).
Just like atoms in a gas scoot about with Brownian motion due to thermal energy, the conductance electrons in a conductor scoot about in a random path thanks to Fermi energy; simplistically put, 'colliding' and bouncing about by means of their charges repelling each other. By the way, this phenomenon of random motion is what is partially responsible for the shot noise associated with an electric current. In this free electron model Electric current is the drift of this electron gas as a whole not the motions of individual electrons. Just as with Brownian motion in a flow of gas, the electrons are moving with, against and sideways in the current and it is only the net overall motion of all the electrons as a whole that makes up the current. To put this into perspective, the drift velocity of electrons in a conductor is on the order of 1 cm/s, the Fermi velocity of individual electrons is about 8 magnitudes higher on the order of 1 miilion m/s. (note order, not close order).
For a more proper introduction to electron transport in conductors see this.
Of course, all this is a classical approximation of what's really going on at the quantum level where all is woo-woo and ju-ju that sane minds cannot even begin to comprehend.
Now, how tunnel diodes work...
* More correctly covalent bonding is more a probabilistic smearing out of the electron between the two atoms that share it than any kind of proper motion. -
Why your brain thinks this does not cut it is because it's the wrong analogy but it's nevertheless close to the truth. The error is in making the analogy flow along a pipe as if that's driven by hitting things. It's not applying momentum to a particle, it's the space the particle takes up in the pipe which in the physical analogy increases the pressure at the start of the pipe, leading to pressure drop along the pipe which leads to flow (i.e it's all really about charge, potential, potential differences with their concomitant electric fields and current).
My issue with the analogy (and any so far) is not with space or momentum, it's a simple logicistic calculation that if I have 100 electrons on one side of a battery and to discharge that battery I need to physically move those 100 electrons to the other side... and that they only move at 1cm/s through the conductor... the battery and conductor are able to complete this operation is a time far shorter than 1 cm/s physically permits.
The pipe, marble analogy seems to suggest that the wire is full of electrons and so when you pop one in one end a displacement travels the length of the copper and one pops out the other end. That's fine, but if you think it through and instead of 100 electrons over a few minutes you want to run trillions and trillions of electrons down the same conductor for 10 years. There simply are not enough electrons in the conductor, so the electrons you add at one end, need to make it all the way to the other end. So the maximum physical transit of electrons is still 1 cm/s.
Put another way, you are still putting electrons in one end and getting them out the other, you surely have to see that if you run that experiement for long enough the first electron you put in, must have made it to the other end. Not unless electrons are simply bunching up at the near end and being fabricated at the far end so they can catch up at 1 cm/s. Run it for years, that just doesn't make sense.
So if it is 1 cm/s then it cannot be physical particle electrons "flowing" from on side of the battery to the other, something else must be happening.
Also did Maxwell not describe everything as universal fields that are present everywhere and his work does not even mention the electron. I might be wrong but did Maxwell's work not pre-date the discovery of the electron?
I can fully understand the effect of an EM field transiting the conductor via the electrons but I'm still stuck at the battery problem as it seems to suggest physical electrons are removed from negative ions at the - terminal and transported to the + terminal.
On conductors and electrons, I believe the important electrons are the D shell electrons. The D shell does not need to be filled completely to have electrons in the higher shells, the metals we know to be good conductors fall into the range on the periodic table that have abundand electrons in the D shells. These electrons are "free" because the atom can share, borrow, lend these electrons and still retain it's chemical energy state. So in something like a copper bar, these D shell electrons form more of an ocean the atom sit within. -
Earthing for a pole of battery is completely useless.
Electricity is NOT particle count, it's energy of particle pressure. The battery is like compressed spring, when you release it, it releases accumulated energy of compression BETWEEN TWO points of spring. If you touch Earth with compressed spring, it won't affect energy accumulated in the compressed spring.
The same, when you connect Earth to one pole of battery it won't affect the charge between two poles of battery. Just because energy is accumulated BETWEEN TWO poles of battery, but not between Earth and one pole of battery
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Put another way, you are still putting electrons in one end and getting them out the other, you surely have to see that if you run that experiement for long enough the first electron you put in, must have made it to the other end.
What reason do you have for this being a problem? If I stuff a red marble in the end of the pipe and keep stuffing marbles, then eventually the red marble will pop out the other end. And?
I really suspect you are trolling here. You are constructing logical absurdities and using them to argue nonsensical positions. -
I really suspect you are trolling here. You are constructing logical absurdities and using them to argue nonsensical positions.
Don't be too quick to judge. Getting the full picture of what's going on - as opposed to just chucking around analogies - takes some really hard thinking that necessarily encompasses the weird world of quantum where commonsense does not apply. Also it encompasses electromagnetic propagation a la Maxwell which is also a mind-bender, and finally you're dealing with very large and very small numbers that are way outside of the range of natural comprehension (avagadro's number 6.02214076×1023 = 60,221,407,600,000,000,000,000 atoms/mole, charge on an electron 1.602176634×10−19 Coulombs = 0.000 000 000 000 000 000 160 217 663 4 Coloumbs and so on). -
My issue with the analogy (and any so far) is not with space or momentum, it's a simple logicistic calculation that if I have 100 electrons on one side of a battery and to discharge that battery I need to physically move those 100 electrons to the other side... and that they only move at 1cm/s through the conductor... the battery and conductor are able to complete this operation is a time far shorter than 1 cm/s physically permits.
They don't move individually at circa 0.1 cm/s, they each individually move randomly 100 million times faster. The 0.1 cm/s is just the net drift velocity of the whole electron cloud as a whole. The drift is caused by an electric field, which propagates at the speed of light in that medium, so the effect of the electric field is felt at the far end of the wire mere nanoseconds after the potential difference is applied.QuoteThe pipe, marble analogy seems to suggest that the wire is full of electrons and so when you pop one in one end a displacement travels the length of the copper and one pops out the other end. That's fine, but if you think it through and instead of 100 electrons over a few minutes you want to run trillions and trillions of electrons down the same conductor for 10 years. There simply are not enough electrons in the conductor, so the electrons you add at one end, need to make it all the way to the other end. So the maximum physical transit of electrons is still 1 cm/s.
Put another way, you are still putting electrons in one end and getting them out the other, you surely have to see that if you run that experiement for long enough the first electron you put in, must have made it to the other end. Not unless electrons are simply bunching up at the near end and being fabricated at the far end so they can catch up at 1 cm/s. Run it for years, that just doesn't make sense.
So if it is 1 cm/s then it cannot be physical particle electrons "flowing" from on side of the battery to the other, something else must be happening.
I can't see where you're having a problem (other than perhaps with scale). If you use a hosepipe, do you expect the water you put in to appear immediately at the other end? No, you expect the water that is already in the hose to pour out first. The net drift of the cloud of water molecules down the pipe takes a few seconds, perhaps minutes, however the individual water molecules are moving much faster (Brownian motion remember), several orders of magnitude faster. Just the same as with an electron cloud in a wire.
The only significant difference is of scale, in copper the charge carrier density (number of conductance electrons per volume) is about 8.5 × 1028 m-3. So a 1m long, 1mm2 cross section wire (~ 17 AWG wire) has 8.5 x 1022 = 85,000,000,000,000,000,000,000 conductance electrons to play with. One amp of electricity requires the flow of 6.24 x 1018 = 6,240,000,000,000,000,000 electrons per second. So that 1m x 1mm2 wire already contains 13,620 amp seconds worth of conductance electrons before you've started. It's a very big pipe, they are very small marbles, they are vibrating very fast and very violently.QuoteAlso did Maxwell not describe everything as universal fields that are present everywhere and his work does not even mention the electron. I might be wrong but did Maxwell's work not pre-date the discovery of the electron?
So? Many correct scientific theories have predicted the behaviour of things that hadn't yet been discovered at the time. Maxwell's equations describe the world of electromagnetism. What is electron transport if it isn't an electromagnetic phenomenon?
The thing that moves the electrons is not electrons being inserted into the wire a la marbles, but electric fields. To understand electric fields and how charge gives rise to electric potential which gives rise to fields you need Maxwell - it is not simple and even when well explained (don't expect that from me, I just about understand it) some people will never 'get' it. Without a mentioning Maxwell, merely stating that it's the electric field from the voltage that makes it all move feels a bit to much like hand waving - so Maxwell gets a mention.QuoteI can fully understand the effect of an EM field transiting the conductor via the electrons but I'm still stuck at the battery problem as it seems to suggest physical electrons are removed from negative ions at the - terminal and transported to the + terminal.
Yes, eventually they are physically moved, via a conductor from one terminal to the other, dragged/pushed along by the electric field. You may be waiting some time for an electron that has left the -ve terminal to eventually reach the +ve terminal. -
What reason do you have for this being a problem? If I stuff a red marble in the end of the pipe and keep stuffing marbles, then eventually the red marble will pop out the other end. And?
I really suspect you are trolling here. You are constructing logical absurdities and using them to argue nonsensical positions.
If you believe the marbles move instantaneously within your pipe, it is you who are constructing logical absurdities.
If the marbles in the pipe are sitting in thick tar that, with all reasonable force, limits them to moving at 1 cm/s and the marbles are 1cm wide, the maximum through put of that pipe is 1 marble per second.
Consider if you had 10 marbles in the pipe and you pop another (11) in the end. Marble 1 falls out. You have marbles 2-11. However for this to repeat again, marble 2 needs to move to where marble 1 previously was and before you can even insert marble 12 you need to wait until they all shuffle along. Everyone needs to move. If that speed is limited you can calculate the maximum through put. It's standard "Queue dynamics"
However Cerberus's comment on scale might be what I was missing.QuoteThe only significant difference is of scale
The marble analogies tends towards a single linear queue of marbles, but a nano-meter cross section of the conductor might have trillions of electrons, so move the cloud forward at 1 cm /s and each nano-meter of "motion" accepts trillions of trillions of electrons at one end and probably makes a similar number available at the other end. It's like running trillions of queues in parallel, multiplying the number of electrons that can transit the conductor per second.
I think that works for me, I think I'm good.
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you can imagine electricity like gas flow and battery as a gas pump. In order to get gas flow you're needs to connect pump output to pump input. If there is a break in the gas pipe (no connection between battery poles), the pump won't be able to make gas flow in the pipe.
It can make some small movement for a shot period of time, but since there is no circular way in the pipe, the pump won't be able to keep gas flow continuously. The same thing with battery. If you connect one battery pole to the Earth, it may lead to some small movement for a short period of time (static potential discharge between Earth and battery pole), but the battery won't be able to keep electron gas flow, since there is no way from one battery pole to another. -
By now the OP is probably cowering in a distant corner somewhere......
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By now the OP is probably cowering in a distant corner somewhere......
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It was inevitable the thread would take this path, since electric current flowing in a circuit isn't as straightforward as most beginners imagine.By now the OP is probably cowering in a distant corner somewhere......
Should have just taken the blue pill instead.
There is no problem with the thread deviating into electrostatics and quantum mechanics, as it will help others, even if the original poster loses interest. -
It was inevitable the thread would take this path, since electric current flowing in a circuit isn't as straightforward as most beginners imagine.By now the OP is probably cowering in a distant corner somewhere......
Should have just taken the blue pill instead.
There is no problem with the thread deviating into electrostatics and quantum mechanics, as it will help others, even if the original poster loses interest.
Removed my post. It was not appropriate. My apologies.