Does current flow through a Battery?

[ejeffrey]

So far, no-one here has dared/tried to counteract what I said about a 'Capacitor',

Because 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.

(which IS basically behaving like a battery,

In 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:

where there is NO actual flow of 'charge' within it, through the Dielectric

So 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

[GlennSprigg]

"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.

Sorry Tim....  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' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

[TimFox]

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 certainly a form of current.

[bdunham7]

I 'guess' I'm taking it to my grave then... but I can NOT accept that there is 'any' CURRENT flow that is 'not' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

What would you call a beam of protons or alpha particles?

[SilverSolder]

"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.

Sorry Tim....  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' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

Here'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 radiation

Q:  Will the coil pick up a signal (indicating that a current is flowing through the middle of it)?

[TimFox]

"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.

Sorry Tim....  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' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

Here'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 radiation

Q:  Will the coil pick up a signal (indicating that a current is flowing through the middle of it)?

An 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.

[TimFox]

I 'guess' I'm taking it to my grave then... but I can NOT accept that there is 'any' CURRENT flow that is 'not' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

What would you call a beam of protons or alpha particles?

For 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.

[TimFox]

I only post trigger warnings when Bessel functions are involved.

[Alex Eisenhut]

I 'guess' I'm taking it to my grave then... but I can NOT accept that there is 'any' CURRENT flow that is 'not' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

What would you call a beam of protons or alpha particles?

Uh, the Strategic Defense Initiative?

[SiliconWizard]

So does current actually flow at all through anything?

[Alex Eisenhut]

So does current actually flow at all through anything?

This flows through me

[TimFox]

So does current actually flow at all through anything?

Yes.

[tszaboo]

which IS basically behaving like a battery,

No it doesn't.

[ejeffrey]

"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.

Sorry Tim....  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' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

Please 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"

[tom66]

So it sounds to me like batteries are really just chemical capacitors.

There is a sense in which this is absolutely true 

Lithium-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.

[GlennSprigg]

I 'guess' I'm taking it to my grave then... but I can NOT accept that there is 'any' CURRENT flow that is 'not' involving
actual 'Electrons', as we  understand today...  and I will never think any other way!   

What would you call a beam of protons or alpha particles?

Errmm...  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! 

[TimFox]

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.

[Doctorandus_P]

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_mass

The 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.

[TimFox]

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.

[GlennSprigg]

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.

I DO generally get what 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 am ONLY
talking about 'Electron-Flow' through 'Electrical Conductors'. And TODAY, we understand that 'Conventional' flow is not correct, and
that 'Current' in the manner for which 'I' speak, involves 'Electrons' from -ve to +ve.  However, even that pedantic Nomenclature is
not relevant, when referring to the lack of 'flow', across an insulating '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, and back to the other 'Side' !   
Still love you though... 

[TimFox]

"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.

[GlennSprigg]

"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.

Oh 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 think
on 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 not
relevant 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 the
other 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 do
not want to waste people's time any more... And I should concentrate my *time* on more relevant contemporary issues I have!! hahaha...   

[TimFox]

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.

[IanB]

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, the average current 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.

[TimFox]

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.