Does current flow through a Battery? - Page 1
Forum section: electronics / general

author: kevin original
author_rank: Contributor
timestamp: October 16, 2021, 03:25:06 am
content: I recall Dave having a discussion about whether or not current flows through a capacitor because the electrons can't make it through the dielectric(unless you let the smoke escape). I've recently been looking into batteries and I've read that electrons do not pass through electrolyte solutions, which boggles my mind. We all know that adding salt of some form to water makes it conductive to electricity and "current flow" but if it is true that electrons do not journey across the electrolytic fluid and it is only the ions that travel between the electrodes then does current really flow through a battery? Perhaps electrons do travel through a battery just hitching a ride on the ion but when all of the ions "run out" the current flow stops. So it sounds to me like batteries are really just chemical capacitors.

author: IanB
author_rank: Super Contributor
timestamp: October 16, 2021, 03:34:20 am
content: Quote from: kevin original on October 16, 2021, 03:25:06 amThere is a sense in which this is absolutely true

author: bdunham7
author_rank: Super Contributor
timestamp: October 16, 2021, 03:38:46 am
content: Quote from: kevin original on October 16, 2021, 03:25:06 amThat's pretty good simplified version of how an Li-ion battery works.QuoteNo, absolutely not.

author: bob91343
author_rank: Super Contributor
timestamp: October 16, 2021, 04:03:09 am
content: Batteries have a lot in common with capacitors. Ions and/or electrons are the means of charge transport in batteries. In capacitors, it's the charge and discharge that 'imitates' current flow.

author: eti
author_rank: Super Contributor
timestamp: October 17, 2021, 12:28:34 am
content: One wouldn't get very far if it didn't - put 4 "D" cells in a Maglite and the current HAS to flow through ALL of the cells.

author: bob91343
author_rank: Super Contributor
timestamp: October 17, 2021, 12:37:53 am
content: The idea here is not whether current goes from cell to cell, but whether it flows internally within the cells. Of course it flows externally but it's not clear what the mechanism is, especially within a capacitor.

author: eti
author_rank: Super Contributor
timestamp: October 17, 2021, 12:42:48 am
content: Well of course it does.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 17, 2021, 02:41:01 am
content: Quote from: kevin original on October 16, 2021, 03:25:06 amCurrent definitely flows through a battery in the form of ionic drift through the electrolyte which can be positive or negative. The electrolyte is not a metal so it doesn't support "free" conduction electrons in the same way as a wire but there is still current flowing.For what it's worth, even if you are so mentally inflexible that you can't consider displacement current a real current (which you absolutely should), current flows through most capacitors. Dave's argument only holds for vacuum capacitors, but most capacitors have a deliberately chosen high dielectric constant material between the plates. Microscopically, the electrons in the dielectric move in response to the applied field and generate a current. Normally we don't think about this and we just lump that into the displacement current along with the displacement due to the vacuum permittivity, but if you are going to be pedantic about it you should at least do so correctly.

author: TimFox
author_rank: Super Contributor
timestamp: October 17, 2021, 02:51:52 am
content: The important difference between a cell or battery and a capacitor is that the voltage across a capacitor is proportional to the charge therein, while the voltage across a cell is close to independent of the charge therein. Therefore, the energy stored in a capacitor is (1/2)QV, but the energy stored in a cell is approximatelyQV, whereQis the charge.Note that a battery is a series connection of cells: the common AA alkaline is a cell, but the common 9 V alkaline is a battery.

author: kevin original
author_rank: Contributor
timestamp: October 17, 2021, 04:08:52 am
content: Thinking a bit more on it. I don't believe the ions are actually accepting or releasing electrons at the electrode. Instead the ions are displacing the electrons at the electrode by their movement towards them and thus attracting/repelling them. So electrons are not actually being moved through the battery(except for the ones bound to the ion). "Current flow" however is the time rate of electric charge. Ions by definition have electric charge even though they are not free electrons. By definition then, electric current does flow through a battery albeit through mechanical action ie. protons are moving with the current.

author: IanB
author_rank: Super Contributor
timestamp: October 17, 2021, 09:35:15 am
content: Quote from: kevin original on October 17, 2021, 04:08:52 amOf course they are.The cell has to remain electrically neutral. Whenever an electron leaves one electrode an electron enters the other electrode to balance it. You can look at this from the electrical circuit's point of view, where the electrons are entering and leaving the electrodes through wires, or you can look at this from the electrolyte's point of view inside the cell, where the electrons are entering and leaving the electrolyte solution. Whichever way you look at it, everything balances, and overall electrons are flowing round the circuit.

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 17, 2021, 12:53:10 pm
content: Quote from: eti on October 17, 2021, 12:42:48 amHmmm... I know what you say sounds logical, but just sticking to Capacitors for a sec, there is no actual 'current' flowinginternallybetween the plates.It just holds a 'Charge', where one side holds an excess of electrons compared to the other side. It's the 'Circuit' connected to such a Capacitor that'transfers' the excess of electrons from one side, and balances it to the other side!! Even with Batteries, this is so, but done chemically though.Say there 'are' 4 batteries in series... you have to think about 'Charge-Relativity' to grasp it all. Again, it's the relative charge difference between the 'cells'that causes a flow from the -ve end of one battery, to the +ve end of the next battery etc, and only when an external circuit is completed! So the END oflast one, flows into the beginning of the first one, via the external circuit. It is not flowing 'internally' within one cell !!

author: ejeffrey
author_rank: Super Contributor
timestamp: October 17, 2021, 10:07:08 pm
content: Quote from: GlennSprigg on October 17, 2021, 12:53:10 pmBatteries are not capacitors.QuoteIt most certainly is.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 18, 2021, 10:13:00 am
content: I had to re-read the definition of electric current before having a word to say, to me it fits batteries and capacitors.Considering self discharge, current even flows more through batteries than elsewhere...(To attempt an answer to the topic question.)

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 19, 2021, 11:05:36 am
content: Regarding the last two answers here... you are mis-interpreting what I was saying.Firstly, I'm NOT talking about imperfections/breakdowns in the real-world, where a Capacitor or Battery may 'leak' internally,and lose some/all of it's charge internally. That certainly happens 'within' the cell, but is unrelated to what I am saying!If the above doesn't occur, then they hold their 'charge' until such time as theExternal Circuitconnected to such devices performsthe 'actual' completion of the path of the Electrons, back to the other side! I don't understand the problem of grasping that ??And the way a 'Battery' discharges, (through an external circuit), is the same as a Capacitor so discharges, but using 'obviously' differenttechnology, as the charge is Chemically Stored instead, not with a 'charge' either side of anon-conductingDielectric. So I stand by mystatement the Electrons flow 'externally' from one side of such devices, and 'back' to the other side. I'm not trying to be silly here ?

author: tszaboo
author_rank: Super Contributor
timestamp: October 19, 2021, 11:19:32 am
content: Current is defined as movement of charged particles.Batteries have a separator. Positive ions go through the separator.Their negative particles, the electrons go through the wire, because they cannot go through the separator.There is a movement of positive particles, so there is current in a battery. Its different than the current we usually see in wires and resistors and whatnot, but it is still current.

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 19, 2021, 11:42:36 am
content: Quote from: tszaboo on October 19, 2021, 11:19:32 amAgain, I know what you are saying too, but it's all a matter of 'nomenclature' and ideas used to understand.Your statement of "Movement of Positive Particles", smacks to me of the 'old' idea, (hence direction arrows etc in Diodes, Transistors, Valves/Tubes),before they realized that it is actually 'Electron' flow, from -ve to +ve, and not the other way around!! My old Instructors (about 50 years ago!), usedto try and explain it away by talking about... "A movement of Positive Holes", in the reverse direction of actual Electrons! Here's how that worked!!..."Put a line of blocks, (electrons!), on the table. Now starting from the right, move the last block to the right a bit. Then move the second block from theright to join the 1st block moved. And then keep doing that with the remaining blocks in the same way". Then they would say... "Notice how the GAPbetween the blocks appears to be moving to the Left! That is the movement of Positive Holes!!". Ggrrrr... Even then at 16, I would pull them up, andtell them to start talking about 'Electrons', and that drawing 'standards' even 'today', should be changed !!!

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 19, 2021, 02:02:35 pm
content: All I was saying is that IMHO what happens in a battery fits the definition of electrical current flow...Although the smiley didn't make it obvious enough the internal leakage comment was a form of humour.In what way would you say that batteries do not fit the definition of "electric current"?

author: tszaboo
author_rank: Super Contributor
timestamp: October 19, 2021, 02:34:17 pm
content: Quote from: GlennSprigg on October 19, 2021, 11:42:36 amIt's the definition of current in "The Art of electronics" page 2. There is no "old" or "new" definition of current. You can also look up the definition of Ampere, (and Coulomb) which is defined as X amount of charge in a second, not X amount of electrons.

author: TimFox
author_rank: Super Contributor
timestamp: October 19, 2021, 02:49:02 pm
content: Once again, I suggest you go to any freshman physics textbook that discusses electrical current.Examples I remember from freshman physics are:1. Flow of electrons through a vacuum from cathode to anode in a vacuum tube.2. Net motion of electrons or holes through a solid.3. Mechanical motion of charged patches on a moving insulating substrate, such as the belt of a Van de Graaff generator.4. "Displacement current" through a capacitor dielectric. This is not a new phenomenon, it was discovered in the 19th Century.5. Net motion of charged ions (both polarities) in a liquid solution.6. Protons moving in a particle accelerator, accelerated by alternating electrical fields in synchrotron cavities.etc.Electrical current was discovered long before the discovery of the electron in the 1897 by J J Cavendish.There is no need at this late date to redefine positive and negative charges and currents, obsoleting centuries of science (except for WW II-era electronics training in the vacuum-tube era).

author: ejeffrey
author_rank: Super Contributor
timestamp: October 19, 2021, 04:38:13 pm
content: Quote from: GlennSprigg on October 19, 2021, 11:42:36 amHoles are completely OT to the question at hand which is electrochemical cells, but even if we redefined positive charge to mean electrons (which there is absolutely no reason to do), we would still have the concept of holes -- they would just be negatively charged. Holes are not an annoying wart that we have to deal with because of the "wrong" charge convention, but an essential concept in semiconductor physics.But in a electrochemical battery we have physical motion of charged ions through the electrolyte. Depending on the battery chemistry these can be positively or negatively charged.You don't have to try to reason about this from first principles or resort to analogies, you can just read about what exactly happens in a battery.I really, really, really wish high school physics teachers would stop saying that "Ben Franklin got the conventional current definition wrong but we are stuck with it" -- this places way to much focus on electrons rather than the idea of fields and net charges which is really what matters. The fact that in metallic conductors the electrons are the mobile charge carriers is irrelevant unless you are studying solid state physics.

author: TimFox
author_rank: Super Contributor
timestamp: October 19, 2021, 04:51:36 pm
content: Exactly. Electricity was discovered and quantified long before a particle that is very important in electricity was discovered and named the "electron".

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 22, 2021, 01:31:45 pm
content: Aaarrgghh.... I 'get' what people are saying, but still think there is a miss-communication of ideas/concepts here...Old Scottish song..."I'll tak the high road and you tak the low road"... Oh well, what ever people feel comfortable with.So far, no-one here has dared/tried to counteract what I said about a 'Capacitor', (which ISbasicallybehaving like a battery,but not chemically), where there is NO actual flow of 'charge' within it, through the Dielectric, and that any 'flow' is EXTERNALthrough anattached circuit, and 'then'backto the other side of the Capacitor??? I do not grasp the problem of this thinking???If I'm wrong, then I'll probably go to my not far off grave believing what I believe, so what does it really matter! hahaha...

author: TimFox
author_rank: Super Contributor
timestamp: October 22, 2021, 02:36:47 pm
content: "Displacement current" was discovered in the 19th Century and is included in Maxwell's Equations to explain the current through a capacitor.Ionic current in batteries is similar to ionic current in salt-water solutions.Current is a more general term than the motion of electrons in a vacuum tube.

author: TimFox
author_rank: Super Contributor
timestamp: October 22, 2021, 04:49:49 pm
content: Here is a thought-experiment to show the importance of displacement current through a capacitor in the real world.1. Set up two parallel plates, each 10 cm by 10 cm, spaced by 1 cm, inside a transparent jar that can contain the sand discussed below.2. With air between the plates,k= 1 (dielectric constant), the capacitance will be approximately 0.9 pF. (Even without a material dielectric, there exists a polarization field between the plates. When we add material below, the polarization increases for a given applied voltage.)3. Connect an AC generator (output impedance 50 ohms) through this capacitor to a 50 ohm load and AC voltmeter. The total circuit impedance is 100 ohms (resistive) plus the reactance of the capacitor.4. At 10 MHz, the reactance of the capacitor is about 18 k and dominates the total impedance of the circuit.5. Now, start adding SiO2powder (sand) to the region between the plates. It is a good insulator, but solid SiO2haskbetween 3.7 and 3.9. Since the powder has a lower density than the solid, assumek= 2.5. As the sand level increases from zero to fill the gap, the capacitance increases from 0.9 pF to 2.2 pF, and the current in the circuit (measured by the voltage across the 50 ohm load) will increase by almost the same factor as the reactance decreases.With these parameter values, the voltage across the capacitor itself is almost constant (since its reactance is much larger than the total resistance of 100 ohms), but the displacement current increases with the increased polarization in the dielectric. Current continuity includes the conduction current through the two resistors and the displacement current through the capacitor.Moral: just as there are many flavors of ice cream, displacement current is one type of the general phenomenon known as "current", along with ionic current, conduction current, beam current, etc.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 23, 2021, 04:02:26 am
content: Quote from: GlennSprigg on October 22, 2021, 01:31:45 pmBecause the title of the thread is "does current flow through a battery". Responding to a description of what is happening with ionic flow inside a battery with "but a battery is basically like a capacitor" is called moving the goalposts and is actually rather rude. It's fine to ask about capacitors as well, but to use that to derail an explanation and then try to go back and claim that your "what about a capacitor" question is evidence that the answer for batteries is wrong is not really OK.QuoteIn that it stores and releases electrical energy, yes. Otherwise, not so much. If you have a problem with the explanations of charge movement in batteries go ahead and ask, but if you don't, just move on.Anyway, given that batteries have already been explained in detail:QuoteSo I don't care to debate whether displacement current is "real" current, but even setting that aside this is technically wrong in most cases.In a vacuum gap capacitor you are correct that there is no charge flow in the gap. But very few real capacitors are made this way. Generally they have a dielectric that has relative permittivity >> 1. A dielectric is just a bunch of positively charged nuclei and bunch of electrons bound to them. Unlike in a metal, the electrons cannot flow over long distances but when an electric field is applied (by charging up the capacitor), each electron moves slightly towards the positive electrode while staying bound to the same area. That is a moving charge and thus a current. How big is that current? The material polarizability is exactly a measure of this charge movement. If you have a capacitor dielectric with relative permittivity 10 and 1 amp RMS is flowing in/out of the capacitor from the external circuit then there is 900 mA of dielectric charge motion and 100 mA of vacuum displacement current. Even if you say the vacuum displacement current doesn't count the other 90% is physical charge movement.We don't normally worry about this. Dielectric polarizability has exactly the same mathematical form as the vacuum permeability. For Maxwell's equations in matter J only refers to "free" current, and the motion of bound charges within a dielectric is just combined with the displacement current into a single term. But if you want to be pedantic, you should at least do so correctly

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 24, 2021, 12:14:48 pm
content: Quote from: TimFox on October 22, 2021, 02:36:47 pmSorryTim.... I love you as a tech contributor here, (I highlighted in BOLD your last sentence of concern)...Again, it seems to be about 'nomenclature' and not about present acceptance of 'standards' ??I 'guess' I'm taking it to my grave then... but I can NOT accept that there is 'any' CURRENT flow that is 'not' involvingactual 'Electrons', as we understand today... and I will never think any other way!

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2021, 02:17:36 pm
content: Electricity and thermodynamics were first treated like hydraulics, involving flow of some kind of fluid, before elementary particles were discovered.Early on, the important difference about electricity was discovered, that it involved opposite charges that could be called positive and negative.Only later were the particles discovered, but current of all kinds and charge carriers (including protons) remained, roughly following the original rules."Displacement current" was added to the inventory of current types in order that current around a circuit, however formed, followed the continuity rules.The point that I persist in making is that electric current is more general than electron flow, although electron motion is certainlya form ofcurrent.

author: bdunham7
author_rank: Super Contributor
timestamp: October 24, 2021, 03:12:11 pm
content: Quote from: GlennSprigg on October 24, 2021, 12:14:48 pmWhat would you call a beam of protons or alpha particles?

author: SilverSolder
author_rank: Super Contributor
timestamp: October 24, 2021, 04:02:04 pm
content: Quote from: GlennSprigg on October 24, 2021, 12:14:48 pmHere's an interesting mind-bending thought experiment for you:1. Grab an air capacitor with two plates.2. Put a flat copper coil between the two plates (e.g. one to 10 turns). Place it flat like the plates, right in the middle of the gap, but not touching the capacitor plates.3. Apply a moderate frequency AC voltage to the air capacitor, say 1KHz, so we don't have to deal with RF radiationQ: Will the coil pick up a signal (indicating that a current is flowing through the middle of it)?

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2021, 04:09:57 pm
content: Quote from: SilverSolder on October 24, 2021, 04:02:04 pmAn interesting thought-experiment (sounds better in German). To be correct, the coil needs to be shielded against the electric field between the plates—this is often done with a few turns of coax, where the magnetic field sensing is done between the two ends of the inner conductor, and the shield is either grounded at one end only, or grounded at both ends with a gap in the center. The AC displacement current between the plates can be calculated from the capacitance (also frequency and voltage), and the emf in the coil follows. An interesting quantitative exercise for the reader.

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2021, 04:15:00 pm
content: Quote from: bdunham7 on October 24, 2021, 03:12:11 pmFor example, the original CERN proton synchrotron has a circumference more than 600 m. Along that path, current is carried by positive particles (usually protons). For practical reasons, the current is pulsed, and the strength of the current pulses is monitored by passing the beam down the axis of sense coils.

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2021, 05:11:12 pm
content: I only post trigger warnings when Bessel functions are involved.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 24, 2021, 05:35:25 pm
content: Quote from: bdunham7 on October 24, 2021, 03:12:11 pmUh, the Strategic Defense Initiative?

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 24, 2021, 06:01:07 pm
content: So does current actually flow at all through anything?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 24, 2021, 06:19:02 pm
content: Quote from: SiliconWizard on October 24, 2021, 06:01:07 pmThis flows through me

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2021, 06:21:33 pm
content: Quote from: SiliconWizard on October 24, 2021, 06:01:07 pmYes.

author: tszaboo
author_rank: Super Contributor
timestamp: October 25, 2021, 03:33:01 pm
content: Quote from: GlennSprigg on October 22, 2021, 01:31:45 pmNo it doesn't.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 25, 2021, 04:45:19 pm
content: Quote from: GlennSprigg on October 24, 2021, 12:14:48 pmPlease be 100% clear here: do you not want to count displacement current as "real" current or do you think ionic drift or proton motion are not "current"?Whether you want to consider displacement current "real" current or not is mostly a matter of application. Charge vs. displacement current are indeed different things, but including displacement current makes KCL exact rather than an approximation and displacement current creates magnetic fields exactly the same way as charge currents. However, charge current is independently conserved quantity so in some equations it appears alone. The correct quantity to use depends on the application.None of that is relevant to batteries which have no displacement current. The current flowing through batteries is by the physical movement of charged particles -- ions that may be positively or negatively charged. Any definition of current that doesn't count this is fatally flawed and has no technical value for any purposes. It makes as much sense as measuring traffic across a bridge and deciding that only blue and grey cars are "real" traffic and other colors like white and red are just mathematical tricks or "matters of definition"

author: tom66
author_rank: Super Contributor
timestamp: October 25, 2021, 09:53:48 pm
content: Quote from: IanB on October 16, 2021, 03:34:20 amLithium-ion capacitors are a really interesting example of this. The properties of both a lithium-ion battery and a capacitor in one device.They have an energy density about half way between supercaps and real Li-Ion batteries but many of the advantages of Li-Ion.Unlike "regular" supercaps they cannot be fully discharged without damage (just like a battery) and their capacity is given as either farads or milliamp-hours.

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 26, 2021, 01:25:23 pm
content: Quote from: bdunham7 on October 24, 2021, 03:12:11 pmErrmm... I would call that either "a beam of protons, or alpha particles"Not talking about 'Photons' or 'X-Ray' s either...I'm talking about 'Electrons' flowing through conductors of electricity... "Coils with AC on them between capacitor plates"...Interesting, but am not talking about the likes of Inductors/Transformers using magnetic field collapses to generate voltage!

author: TimFox
author_rank: Super Contributor
timestamp: October 26, 2021, 02:08:10 pm
content: I stand by my comments above about the different kinds of electrical current.(In theoretical physics, the term "current" is applied to other phenomena, as well, but we are all talking about electrical current here.)Since matter in bulk is damned close to neutral (electrically), the effects of current are generally more important than those of charge, since a large current can flow in a neutral-charge conductor.But through all of this is the requirement of continuity: the current changes type or carrier from place to place, but always goes somewhere.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 27, 2021, 08:59:04 pm
content: I'm not aware that anybody has yet seen an electon.They're quite small and elusive.It does have mass though:https://en.wikipedia.org/wiki/Electron_rest_massThe idea of an electron as a particle that travels through an conductor is a handy model but if you want to go nitpicking you have start with defining what you mean by "current".This is also important if you want to make models of any HF electronics. Transmission lines, effects of GND planes striplines, etc.At some point the model of particles moving though an conductor is not good enough anymore, and you have to start working with the electromagnetic field surrounding the electron. The electons themselves may not pass the isolation barrier in a capacitor, but the electric field surrounding them certainly does pass to the other side. Whether you want to call that "current" or "cheating" is moot to me.

author: TimFox
author_rank: Super Contributor
timestamp: October 27, 2021, 09:14:52 pm
content: My point of view for "normal conduction current" is that is a very slight tendency of an enormous number of conduction-band electrons in the metal to move in the direction of the arrow, superimposed on their normal random thermal motion. The random component has zero mean, even though it has a macroscopic statistical deviation.

author: GlennSprigg
author_rank: Super Contributor
timestamp: October 28, 2021, 12:16:53 pm
content: Quote from: TimFox on October 26, 2021, 02:08:10 pmIDOgenerallygetwhat you are saying, Tim. And the point raised by 'Doctorandus_P' above, saying..."and you have to start working with the electromagnetic field surrounding the electron", and..."The electrons themselves may not pass the isolation barrier in a capacitor, but the electric field surrounding them certainly does",is an interesting phenomena to think about!!! , but really only re-enforces what I'm talking about.In your last statement, I highlighted in 'Red' what concerns/confuses me... (not sure what you meant by 'Carrier' there too).What about 'Eddy' Currents, flowing in a circular fashion within a piece of metal? But not really 'going' anywhere?I'm not taking the word 'Current' in any other context though here... Not talking about Water-Current, or Air-Currents. I amONLYtalking about 'Electron-Flow' through 'Electrical Conductors'. And TODAY, we understand that 'Conventional' flow is not correct, andthat 'Current' in the manner for which'I' speak, involves 'Electrons' from -ve to +ve. However, even that pedantic Nomenclature isnot relevant, when referring to the lack of 'flow', across aninsulating 'Dielectric'. I don't care if they are called 'Electrons' or 'WTF's',I can't understand the confusion about the 'Flow' being external in a circuit, andbackto the other 'Side' !Still love you though...

author: TimFox
author_rank: Super Contributor
timestamp: October 28, 2021, 01:49:09 pm
content: "Carrier" is short for "charge carrier", such as electron, proton, sodium ion, etc."Eddy currents" are "regular" conduction currents with a particular geometry, "going around".Again, it was discovered very early that electricity, as opposed to gravitation or other effects, involved two opposite charges: the decision was made to name "vitreous" electricity (rubbing silk on glass) as positive and "resinous" electricity (fur on amber) as negative. This is a convention or definition, not a mistake. Much later, the elementary particle with a negative charge was discovered and named the electron. Currents continued to flow.The Van der Graaf generator with a beam of alpha particles down the tube is an example of a closed circuit where different branches of the circuit involve the flow of different charge carriers.In an electrolytic cell (like a battery, but with noble-metal electrodes that do not react chemically with the solution), when you dissolve NaCl powder in the water, the molecules dissociate into Na+and Cl-ions that then move through the solvent (water) in opposite directions when voltage is applied to the electrodes, but since they have opposite charge the ionic current flows in the same direction. Similarly, when you dissolve HCl gas into water to make hydrochloric acid, the solute dissociates into H+, which is a simple proton, and Cl-, a negative chlorine ion.Obviously, flow of electrons is an electrical current, but I disagree about limiting the definition of electric current to only that charge carrier.I keep repeating myself, but the definition of electrical current with possible charge carriers was in the first week or so of my freshman college course in electricity and magnetism, and it remains with me 50 years later.

author: GlennSprigg
author_rank: Super Contributor
timestamp: November 03, 2021, 02:03:23 pm
content: Quote from: TimFox on October 28, 2021, 01:49:09 pmOh no!! I've come back again!!! hahaha...Dear Tim, I never wanted to "win" re: this topic, and I know you were not accusing me as such, but I'm still thinking that you/(others) are not *wrong*but on another tangent/thought/statement that I was/am on?? I'm trying to understand (and mostly do!) what you are saying, (again), but please thinkon a different tangent to where your mind is at. Firstly, OK, batteries are more complex a discussion, but please think about *just* a capacitor for now...Firstly, for the sake of the discussion, let's ignore whether *current* flows from -ve to +ve or visa-versa. Don't care. Let's ignore "naming conventions"all together!! In your 1st line above, you said... "Carrier" is short for "charge carrier", such as electron, proton, sodium ion, etc." The Carrier is notrelevant to me, but what it is Carrying is! So you have a Sodium-Ion in solution, it could be anything, but it is carrying (in this case) a Negative charge,meaning there is an excess Electron there, and *that* is what actually Flows! A Positive-Ion has an Electron deficiency, but It's still not relevant to me??A 'perfect' capacitor could hold a charge indefinitely, as there is no Circuit (except atmosphere!). You need to connect that capacitor into an external circuit,(or short-circuit it it with a wire), for the 'Electrons', (sorry, thing-a-ma-whats-its), to travel externally in order to finally return to the *deficiency* on theother side of the capacitor?? There is nothing Flowing internally through the dielectric?? I can not fathom why this is hard to imagine/explain??You are of course an intelligent man, but I seem to lack the ability to explain what 'I' mean here?? I know I will have to let this go though, because I donot want to waste people's time any more... And I should concentrate my *time* on more relevant contemporary issues I have!! hahaha...

author: TimFox
author_rank: Super Contributor
timestamp: November 03, 2021, 02:19:16 pm
content: Displacement current in the capacitor is an interesting concept, and you are within your rights to consider it different from conduction current.Since we are interested in circuits in this forum, displacement current helps to understand current continuity in complex circuits.What I find most interesting in the basis of electricity is that there are two types (polarities, natures) of charge: we call them positive and negative.Electrons have negative charge, but positive charge is not merely the absence of electrons.In nature, protons, alpha particles, and lots of exotic particles known to high-energy physics inherently have a positive charge, with no electrons involved.If we dissolve HCl gas in water to make hydrochloric acid, it dissociates into positive protons and negative Cl-ions.Again, this is different from gravitation, where all particles have positive gravitational mass.

author: IanB
author_rank: Super Contributor
timestamp: November 03, 2021, 03:08:49 pm
content: There is an interesting parallel here with my field of chemical engineering.A chemical plant is a little bit like a big and complex electrical or electronic system, with pipes instead of wires. An electrical schematic and a process schematic look superficially very similar.When simulating a chemical plant, it is common to work with a static, or steady state analysis, where nothing is changing with time. This is useful for design. This analysis is somewhat different from a dynamic analysis, where there are transients and everything is moving.Now, if we jump back to the electrical world, and consider the static or steady state analysis of a circuit, we should discover that the current through a capacitor is zero (unless it leaks). Furthermore, in an AC circuit, theaveragecurrent over time should be zero as well.So one might in fact argue that current does not flow through a capacitor, when viewed in a certain way.

author: TimFox
author_rank: Super Contributor
timestamp: November 03, 2021, 03:40:08 pm
content: Except that when AC flows through a resistor, the average current over time is also zero. (The difference is that a resistor's current, in general, can certainly have a DC value.)In normal analysis, the DC component of anything is the mean value over time, and what is left is the AC component that must have zero mean value over time since the mean value was absorbed in the DC component.

author: VK3DRB
author_rank: Super Contributor
timestamp: November 05, 2021, 12:07:37 pm
content: The northern hemisphere is UP on conventional maps, and Australia is down under. It is only that way by convention - nothing else; and the world would have turned out the same. Similar for conventional current flow versus the "flow" of electrons. We could have easily had everything the opposite way around in our thinking and everything would work just as well.

author: TimFox
author_rank: Super Contributor
timestamp: November 05, 2021, 01:02:45 pm
content: Yes, the two poles (north and south) have physical meaning and either one could be defined as "up". Choosing any other point on the sphere (e.g., London) as the "pole" for spherical co-ordinates works for aviation maps local to Heathrow navigation, but would not work generally.

author: GlennSprigg
author_rank: Super Contributor
timestamp: November 06, 2021, 11:53:48 am
content: Quote from: IanB on November 03, 2021, 03:08:49 pmExactly...I KNOWeveryone here knows how a capacitor works in general, that's why I can not grasp why some people here are confusing what I'm saying,with something else??? I keep repeating thatforgettingabout all naming conventions, and thedirectionof flow of what ever it is, that it is the attachedexternal circuitthat results in theflowofwhateverfrom one side, andbackto the other side!!?? , and sonotthrough thedielectric??!!I'm convincedI must be going mad, hahaha... and think about 'Light' being the absence of 'Darkness' or something...Sorry folks...