Earthing negative pole of battery

[Jr.Maxwell]

I have a question where I cannot find a good answer for,

What are the risks of earthing the negative pole of a 12V battery? I think what will happen is that the battery keeps on discharging. Am I right? and Im I missing something?
Thank you for your time.

[Gyro]

You're kidding, right? [EDIT: Too harsh, sorry.]

Where is the circuit path between the positive to the negative poles of the battery? If there's is no current path then there's nothing to discharge the battery.

[Brumby]

Using the words you have, your question does not make much sense at all.

Draw a picture and show us the situation you have in mind.

[SoundTech-LG]

So, try disconnecting earth, and connect a huge mast antenna to the + terminal. It could eventually get a huge charge, at no charge. Just be at least 100 feet away at all times.

[Ysjoelfir]

Using the words you have, your question does not make much sense at all.

Draw a picture and show us the situation you have in mind.

I agree. To be precise: The way you describe it, you want to connect the negative pole of a battery to earth, while nothing is connected to the plus pole. If that is what you are asking - go on, nothing will happen, since you have no path for the current to flow between the pos and neg battery terminal. It all depends on what your intention in doing so is.

[gbaddeley]

Can you provide more context? What else is connect to neg and pos terminals of the battery? To discharge via earth, there would need to be a DC circuit path from neg to earth to pos.

[paulca]

I expect he just wants to ground reference his DC supply.  This would be akin to the ground referenced DC systems in solar setups.  So he gets 0-12V DC with 0V being Earth referenced rather than floating.

But I suppose we are right to confirm this.

[Nerull]

I expect he just wants to ground reference his DC supply.  This would be akin to the ground referenced DC systems in solar setups.  So he gets 0-12V DC with 0V being Earth referenced rather than floating.

But I suppose we are right to confirm this.

I have encountered people who have been told that the ground is an infinite electron sink in physics classes and think that this means that if you connect something to ground all the electrons flow out of it.

[Brumby]

I have encountered people who have been told that the ground is an infinite electron sink in physics classes and think that this means that if you connect something to ground all the electrons flow out of it.

Hmmm...  That would explain the question.

That's not unreasonable for static electricity and lightning, but it is really negligent for such a statement to be made without clear qualification.

[Zero999]

You're kidding, right?

Come on, this is the beginners section!

I have encountered people who have been told that the ground is an infinite electron sink in physics classes and think that this means that if you connect something to ground all the electrons flow out of it.

Hmmm...  That would explain the question.

That's not unreasonable for static electricity and lightning, but it is really negligent for such a statement to be made without clear qualification.

I think that's sensible. The self-capacitance of the earth is 710µF, which is massive, compared to everyday objects which will be in the hundreds of pF, so it can indeed be seen as an infinite source/sink of electrons.

What's missing from this explanation is the conservation of charge and that it's relative. You can connect a battery's negative terminal to an object with a limitless supply of electrons, but the current will not flow continuously. A current will flow, but only until the battery and earth have equal charge. Now I'm aware that statement is probably confusing, since the battery might have several Ah of charge, but that refers to the charge between the terminals.

Forget the battery for now and consider a capacitor, say 1000µF or 1mF. Charge it to 10V. Connect the negative place to earth and only a current will flow for a short period of time. Now disconnect the negative plate from earth and connect the positive plate to earth, again a current will flow for an instant. Disconnect the positive plate and reconnect the negative plate and a short current pulse will flow again. If the previous steps are repeated indefinitely, the voltage on the capacitor will fall to 0V. The reason for this is the capacitor has a self-capacitance, which is not normally specified on the component, or data sheet. The value marked on the can is the mutual capacitance, between the two plates of the capacitor. The self-capacitance depends on the physical dimensions of the capacitor.

Now let's go back to the battery, if we leave it floating, with neither the anode nor cathode, earthed and connected an oscillator circuit up to it. If we connected the output of the oscillator to earth, a current will flow, depending on the specific capacitance of the battery, the voltage and frequency of the oscillator.

[Jr.Maxwell]

Hello again,

Thank you all for taking the time to answer my question, I realise now that I need to work on how I present my questions haha. This question is a pure hypothetical question meant to further enlarge my understanding of the earthing concept. I feel asif I'm having problems understanding the earthing concept.

I understand that one needs to reference metal enclosures of equipents to earth to prevent dangerous situations from happening, but batteries? Should one reference them to earth as well? I can see the point of earthing the metal enclosure of a circuit , but what hapens if I ALSO earth the battery in the same circuit?

What I meant to say in a more practical way was: Say I have a 12V DC circuit powered by a battery. If I reference the 0V of the battery to earth instead of keeping it flooting, what would happen? will current flow from plus to earth discharing the battery? Is it even wise to reference the 0V of a battery to earth? In this same circuit I have earthed the metal enclousure of the circuit.

Sorry for not being clear the last time, I do wish to understand this concenpt.   If There is any selfstudy I can do to understand this concept, point me to it haha:)

[Zero999]

Hello again,

Thank you all for taking the time to answer my question, I realise now that I need to work on how I present my questions haha. This question is a pure hypothetical question meant to further enlarge my understanding of the earthing concept. I feel asif I'm having problems understanding the earthing concept.

I understand that one needs to reference metal enclosures of equipents to earth to prevent dangerous situations from happening, but batteries? Should one reference them to earth as well? I can see the point of earthing the metal enclosure of a circuit , but what hapens if I ALSO earth the battery in the same circuit?

In the case of mains powered equipment, the mains power supply is already referenced to earth, to prevent it from floating, at much higher voltages, relative to earth, due to something like a lightning strike. If a piece of equipment has a conductive case, it needs to be earthed, so the user doesn't receive a shock, if a fault develops, which causes the case to become connected to the mains. There are of course exceptions, such as when all the electrical circuits inside the case are enclosed in an insulating shield, which makes it impossible for the case to become live, if a wire breaks off.

In the case of a battery operated device, there is no requirement for the case to be connected to earth or the battery. Quite often the battery's negative terminal is connected to the case, because it improves screening and reduces interference.

What I meant to say in a more practical way was: Say I have a 12V DC circuit powered by a battery. If I reference the 0V of the battery to earth instead of keeping it flooting, what would happen? will current flow from plus to earth discharing the battery? Is it even wise to reference the 0V of a battery to earth? In this same circuit I have earthed the metal enclousure of the circuit.

Sorry for not being clear the last time, I do wish to understand this concenpt.   If There is any selfstudy I can do to understand this concept, point me to it haha:)

The short answer to this question is no current will flow, without a return path to the battery. There needs to be a conductive path, between the anode and cathode of the battery, in order for a current to flow and simply connecting one battery terminal to earth, will not cause this to happen.

The long answer is, the total charge on the whole battery never actually changes, as it's "discharged". The entire battery contains the same number of electrons, irrespective of its state of charge. When the battery is discharged, electrons flow from the cathode, to the anode of the battery. When the battery is charged, an external voltage source is applied which moves the electrons back from the anode, to the cathode of the battery.^{*SEE EDIT BELOW}

Charge is relative. If we add or remove electrons to the entire battery, then it will become electrostatically charged, with respect to the surrounding environment, but this would not affect the difference in charge between the anode and cathode of the battery. A 1Ah battery would power a circuit for the same length of time, if we removed or added electrons from the entire battery.

EDIT:
When the battery is charged, the same electron doesn't travel from the cathode, through the circuit and back tot the anode. The electric field pushes electrons out of the cathode, repelling other electrons in the conductor. Eventually an electron pushes out of the other end into the anode of the battery. The electrons themselves move very slowly, yet the time between the switched closing and the the current flowing through the circuit is extremely short.

A good analogy for this is, imagine a straight line of snooker balls, each touching one another. Gently tap the first one and the balls themselves will only move slowly, yet the time between the first ball and last ball moving will be almost instant.

[Jr.Maxwell]

 :)Thanks, that made things clear

[Brumby]

Excluding static electricity....

The short answer to this question is no current will flow, without a return path to the battery. There needs to be a conductive path...

This requirement applies to all electrical circuits - AC, DC, battery or otherwise - the word 'circuit' being a big clue!

In the case of mains powered equipment, the mains power supply is already referenced to earth

... which is done by having one side of the electricity supply connected to the dirt under your feet (aka Earth or Ground) usually by a long metal rod driven into it.  It is this act which defines that side as the "Neutral".

These are some key reasons why this is done:

to prevent it from floating, at much higher voltages, relative to earth, due to something like a lightning strike. If a piece of equipment has a conductive case, it needs to be earthed, so the user doesn't receive a shock, if a fault develops, which causes the case to become connected to the mains.

Where many people get confused is the "mystery" of the Earth connection.  There is nothing special about this - just that it is not as obvious as a wire.  The simple fact is that an Earth connection is nothing magic, but a simple, real and deliberate human thing.

[Gyro]

@Jr.Maxwell, thanks for clarifying your question, and sorry that my first reply was sharp.

I find it useful to consider a battery as a simple chemical reaction (that's what it is internally) rather than a holder of electrons or whatever. The only important thing is that the reaction is 'suspended' and cannot proceed while there is no external connection between the Anode and Cathode, it needs electrons to move from one to the other. Once that connection is made, current flows and the reaction can continue. The speed of the reaction depends on the amount of current that the circuit allows to flow. In the case of a direct short circuit, the reaction will complete very quickly and the battery is quickly dead. Thinking about it like this avoids awkward thoughts about electrons leaking to earth or whatever, the only thing that matters is that connection allowing the reaction to continue.

Just one side point, not relevant to understanding but for reference:

I understand that one needs to reference metal enclosures of equipents to earth to prevent dangerous situations from happening,

Mains equipment, especially consumer items, quite often have metal enclosures that are not referenced to earth. This is done by very careful design and testing to ensure that there is tightly specified double 'layer' insulation between the mains and the enclosure, that cannot be accidentally breached by accident, wires coming loose etc. I only mention it because you may come across such items in the future.

[Jr.Maxwell]

Thanks for the insight !

[Gregg]

As Brumby pointed out, you should always consider the complete circuit and what the ramifications of each part of the circuit may be.  It really helps to understand anything electrical.
Next consider what is the source of power; things like a battery, a transformer, mains, generators etc.  Then consider the possible results of grounding one or more parts of the power source and how that may be helpful or even disastrous.
When considering power sources, consider how isolated they really may be.  For instance, your battery is isolated until you connect a charger that may have a ground reference to one of the battery connections.  A transformer can have isolated secondary windings that can be ground referenced is several ways, such as a center tap or one leg; but an autotransformer has one leg  of the output referenced to the primary.
I’ve known power focused electrical engineers that specialized in grounding; there is a lot more to it than meets the eye.
Telco 48 VDC systems are generally positive ground.  I’ve been told it had something to do with minimizing battery terminal corrosion, but I doubt it matters much with modern batteries that are sealed much better than the old fashioned glass jar flooded lead acid ones. The positive ground system did mess with the heads of a number of telco techs.

[paulca]

The long answer is, the total charge on the whole battery never actually changes, as it's "discharged". The entire battery contains the same number of electrons, irrespective of its state of charge. When the battery is discharged, electrons flow from the cathode, to the anode of the battery. When the battery is charged, an external voltage source is applied which moves the electrons back from the anode, to the cathode of the battery.

Not pretending to understand what I'm talking about here, but what you wrote is what I thought actually happened, until someone pointed out to me that the propagation rate of electrons in a conductor like copper is extremely slow.  Like 3cm/minute or something.  Instead it is the electric field moving through the electrons that carries the current, sort of like a wave.  It also relates to the whole skin effect thing and why sharp bends/traces lead to EMF/RF emission and so on.

So this left me wondering how that applies to batteries which are effectively just ion pumps.

[frogg]

Please define "Earth".

Are you talking about literally sticking a pole into the ground (RF or building electrical wiring) or are you using "Earth" to mean "common ground"?

[Zero999]

The long answer is, the total charge on the whole battery never actually changes, as it's "discharged". The entire battery contains the same number of electrons, irrespective of its state of charge. When the battery is discharged, electrons flow from the cathode, to the anode of the battery. When the battery is charged, an external voltage source is applied which moves the electrons back from the anode, to the cathode of the battery.

Not pretending to understand what I'm talking about here, but what you wrote is what I thought actually happened, until someone pointed out to me that the propagation rate of electrons in a conductor like copper is extremely slow.  Like 3cm/minute or something.  Instead it is the electric field moving through the electrons that carries the current, sort of like a wave.  It also relates to the whole skin effect thing and why sharp bends/traces lead to EMF/RF emission and so on.

So this left me wondering how that applies to batteries which are effectively just ion pumps.

You're right, as the battery discharges, the same electron going out of the cathode, doesn't flow through the circuit and back to the anode. I apologise for implying that was the case.

Linking and explaining microscopic/quantum phenomena to the macroscopic world is difficult. I won't pretend to fully understand QED, because it's not something I've studied formally.

The simplest way I can think of describing it is, the electric field created by the electrochemical reaction in the battery, pushes an electron out of the cathode, respelling electrons in the conductor connected to it, until an electron at the other end is pushed into the anode. Think of a tube filled with marbles. Push a marble in one end and the marbles inside it will move along, pushing another marble out of the other end.

[Brumby]

Please define "Earth".

Are you talking about literally sticking a pole into the ground (RF or building electrical wiring) or are you using "Earth" to mean "common ground"?

This is a good question - and it is something worth asking by anyone who isn't sure in any given situation.  It could even be argued that the term "common ground" might be better phrased differently - eg "common" or "common connection" as the word 'ground' can be synonymous to 'earth'.

This confusion will settle down as you become more experienced in dealing with such circuit topology.  Keep paying attention and you will 'get it'.

[paulca]

Linking and explaining microscopic/quantum phenomena to the macroscopic world is difficult. I won't pretend to fully understand QED, because it's not something I've studied formally.

The simplest way I can think of describing it is, the electric field created by the electrochemical reaction in the battery, pushes an electron out of the cathode, respelling electrons in the conductor connected to it, until an electron at the other end is pushed into the anode. Think of a tube filled with marbles. Push a marble in one end and the marbles inside it will move along, pushing another marble out of the other end.

I've been watching hours and hours of physics videos and lectures recently and I get the feeling that they don't really understand how their different models of things actually interact.  Certainly between the "classical" physics and the "quantum" paradigms there are issues where they collide.

In your example - marbles - the electrons still have to move at the speed of light.  It's like the thought experiment if you had a steel bar 1 light year long and hit it with a hammer would the motion travel instantaneously and thus breach the speed of light, but ... no.  the shock travels through the atoms in the electric field at the speed of light.

So in the case of charge travelling in a conductor, it can't be the "particle" electrons moving.  I has to be the charge moving as eletromagnetic waves via the wave like electrons.  More free electrons means easier transfer of those fields between them.  But that leaves the question of what state of an electron records the fact it has interacted this way or not?  Is it just a "virtual" particle exchange in that each electron receives photons of electric field which it immediately releases again and they exchange them down the line.

ElectroBOOM on YouTube (not exactly academic) mentioned something though.  Similar to the steel bar thought experiment, if you consider the electrons as a line (similar to your marbles) and you thump one end with a charge the shockwave travels rapidly though them while the individual electrons do not move much at all.

It still begs the question... In classical physics we say a battery moves electrons from - ions to the + ions on the other side of the electrolyte via the circuit.  If this is the case, and electrons travel so slowly, how is it possible to balance those ions (discharge the battery) so quickly. The slow propagation rate of particle electrons in a conductor makes it impossible to move all the electrons from one side to the other quick enough.  So maybe they don't actually move along the conductor at all.  Do they even propagate through the electrolyte when you charge the battery?

Maybe we should move this to a more general forum.

I want to say, that, no, I don't really understand what I'm talking about.  I also get that physics uses equations which explain things reliably so we can make the predictions of how the world works, but they are analogous models of reality and reality might be very different.  We still use Newtonian gravity because it works and particle physicists still refer to gravity as a "force" when the apex theory of relativity says it's not.  It's only when you try and use multiple sets of these models together that the "WTF!?" moments emerge. 

[Zero999]

Linking and explaining microscopic/quantum phenomena to the macroscopic world is difficult. I won't pretend to fully understand QED, because it's not something I've studied formally.

The simplest way I can think of describing it is, the electric field created by the electrochemical reaction in the battery, pushes an electron out of the cathode, respelling electrons in the conductor connected to it, until an electron at the other end is pushed into the anode. Think of a tube filled with marbles. Push a marble in one end and the marbles inside it will move along, pushing another marble out of the other end.

I've been watching hours and hours of physics videos and lectures recently and I get the feeling that they don't really understand how their different models of things actually interact.  Certainly between the "classical" physics and the "quantum" paradigms there are issues where they collide.

In your example - marbles - the electrons still have to move at the speed of light.

No they don't. The marbles themselves move very slowly, yet the marble pops out of the other end almost instantaneously.

It's like the thought experiment if you had a steel bar 1 light year long and hit it with a hammer would the motion travel instantaneously and thus breach the speed of light, but ... no.  the shock travels through the atoms in the electric field at the speed of light.

All analogies have their limits. In the case of a steel bar, struck by a hammer, the shock travels at the speed of sound. The same also applies to the marbles, assuming they're in physical contact with one another, although I think it will be slightly slower because there will be tiny gaps between them. In both cases the shock or motion propagates in a wave like manner.

So in the case of charge travelling in a conductor, it can't be the "particle" electrons moving.  I has to be the charge moving as eletromagnetic waves via the wave like electrons.  More free electrons means easier transfer of those fields between them.  But that leaves the question of what state of an electron records the fact it has interacted this way or not?  Is it just a "virtual" particle exchange in that each electron receives photons of electric field which it immediately releases again and they exchange them down the line.

ElectroBOOM on YouTube (not exactly academic) mentioned something though.  Similar to the steel bar thought experiment, if you consider the electrons as a line (similar to your marbles) and you thump one end with a charge the shockwave travels rapidly though them while the individual electrons do not move much at all.

It still begs the question... In classical physics we say a battery moves electrons from - ions to the + ions on the other side of the electrolyte via the circuit.  If this is the case, and electrons travel so slowly, how is it possible to balance those ions (discharge the battery) so quickly. The slow propagation rate of particle electrons in a conductor makes it impossible to move all the electrons from one side to the other quick enough.  So maybe they don't actually move along the conductor at all.  Do they even propagate through the electrolyte when you charge the battery?

The conductor is a transmission line and the same is true for a long steel bar, being struck at one end. The steel bar will only move a tiny amount, relatively slowly, compared to the speed at which the shock will travel from one end to the other.

[IanB]

I find it useful to consider a battery as a simple chemical reaction (that's what it is internally) rather than a holder of electrons or whatever.

This is a very important insight. Actually all chemical reactions involve the movement of electrons. A battery (an electro-chemical cell) is just a special device for capturing the moving electrons from a reaction and diverting them out through the electrodes and wiring. An interesting feature of a battery is that if you don't let the current flow then the chemical reaction is stuck in "suspended animation" and cannot move forwards. (Except for self-discharge and shelf life--the reaction still tends to proceed slowly even if the external current isn't flowing.)

[paulca]

I've been up and down the Internet trying to get a satisfactory answer for this and the concensous answer seems to be ...

Charge (or current depending on your pedantry) does not flow as electrons, it's flows as EM fields between electrons.

However 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.

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. 

It also opens questions about charge and the relationship to electrons.  If Electrons are a "carrier of charge", that suggests an electron can be low charge or high charge, but ... asides not making any sense.  I have never seen anything describing an electron this way.  I have seen electrons having state in that they can be excited into a higher orbital or a lower one by quantum jumps, but not charge.

What I mean is... if you have one of the electrons sitting in the conductor minding it's own business and it gets hit by a photon of EM as the current is "flowing",  at that instant in time, how would you then describe it's state to denote it has received such a photon and is likely to emit one?  Feynman diagrams and virtual particles?

It sounds easier to describe it as an EM wave flowing through the combined electron field of the conductor.... still leave me stuck on the battery though.

[Gyro]

Probably worth asking the OP whether he's passed through understanding and into a world of infinite quantum darkness about now.

[IanB]

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).

However 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.

[Cerebus]

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...

[Brumby]

Probably worth asking the OP whether he's passed through understanding and into a world of infinite quantum darkness about now.

I'd put money on it.

[Jwillis]

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 .

[Cerebus]

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.

[paulca]

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.

[radiolistener]

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

[IanB]

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.

[Cerebus]

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).

[Cerebus]

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.

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.

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.

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?

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.

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.

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.

[paulca]

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.

The 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.

[radiolistener]

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.

[Brumby]

By now the OP is probably cowering in a distant corner somewhere......

[Cerebus]

By now the OP is probably cowering in a distant corner somewhere......

 

[Zero999]

By now the OP is probably cowering in a distant corner somewhere......

Should have just taken the blue pill instead.

It was inevitable the thread would take this path, since electric current flowing in a circuit isn't as straightforward as most beginners imagine.

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.

[Ground_Loop]

By now the OP is probably cowering in a distant corner somewhere......

Should have just taken the blue pill instead.

It was inevitable the thread would take this path, since electric current flowing in a circuit isn't as straightforward as most beginners imagine.

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.