The source of the electric field of a battery?

[cele]

If you place a zinc / copper battery it will create an electric field pointing from the copper to the zinc and my question is this what makes this electric field , the zinc pushes electrons in the circuit and never "stays" negatively charged for an electric field to be created same for the copper plate i am confused about this whole electric field between the plates at the electron level if you could go in details about how do they create an electric field that would be great .
I think the reason could be related to why an electric field is uniform inside a wire.
.

 

[anorlunda]

i feel like i understood more just by asking my self the question.

A question well asked is half answered.

I think the answer you seek is not a question of electric fields but rather chemistry. Get started with this article.
https://en.wikipedia.org/wiki/Electrochemistry#Principles

 

[cele]

A question well asked is half answered.

I think the answer you seek is not a question of electric fields but rather chemistry. Get started with this article.
https://en.wikipedia.org/wiki/Electrochemistry#Principles

Thanks i already know oxidation and reduction i am just having trouble connecting it with the idea of electric fields :)

 

[gleem]

A force field may seem more intuitive but understanding complex systems it is often better to start by considering energy and potential differences .

 

[cele]

A force field may seem more intuitive but understanding complex systems it is often better to start by considering energy and potential differences .

thanks, i already know potential differences in an electric field and i want to know what "creates" this electric field between the copper and zinc plate in relation with oxidation and reduction of them at the electron level

 

[cele]

A force field may seem more intuitive but understanding complex systems it is often better to start by considering energy and potential differences .

thanks, i already know potential differences in an electric field and i want to know what "creates" this electric field between the copper and zinc plate in relation with oxidation and reduction of them at the electron level

 

[DaveE]

In order for the electrons to leave the battery and flow through an attached circuit there must be electric field (i.e. voltage) developed in the battery to overcome the resistance in the circuit. A simple model is that there are an unlimited number of electrons available from the battery, but the rate that they can leave is determined by the resistance of the circuit. For more to leave the battery would need to develop more voltage.

 

[gleem]

Electric charges are still the source of electric fields. Why does one type of atom give up its outer electrons to another?

 

[hilbert2]

thanks, i already know potential differences in an electric field and i want to know what "creates" this electric field between the copper and zinc plate in relation with oxidation and reduction of them at the electron level

It's because it's thermodynamically favorable for the electrons to flow to that direction, it increases the entropy of the system and surroundings. Someone may ask, "how does the zinc plate know about the presence of the copper plate from a distance?", but this is explained by the fact that even a really small excess of positive or negative charge somewhere is able to create a noticeable electric field.

 

[hutchphd]

It's because it's thermodynamically favorable for the electrons to flow to that direction, it increases the entropy of the system and surroundings. Someone may ask, "how does the zinc plate know about the presence of the copper plate from a distance?", but this is explained by the fact that even a really small excess of positive or negative charge somewhere is able to create a noticeable electric field.

But the controlling electric fields develop at the interfaces between the ~liquid electrolyte and the metal electrodes. The flow of ionic constituents in the electrolyte, driven by chemical processes, is balanced by the contervailing flow of electrons in the attached wire to maintain a dynamic equilibrium. If the flow stops the chemistry stops. I've never found it useful to worry about the detailed fields inside the battery...for instance the voltage is essentially independent of geometry.
Of course there is an entire branch of chemistry devoted to such details!

 

[cele]

Thanks for your answers so is it right if i say that the electric field is created by the rate of flow of charges from the negative terminal to the positive terminal ? and if we find materials that have a higher potential difference it means they offer a higher rate of flow for the same recistance ?
Or are the electric field and the rate of flow of charges the same thing ?

 

[cele]

an other post in this forum says "Basically, the battery's voltage depends on how easily your chosen chemicals oxidise or reduce. If redox reactions happen easily, then the voltage is higher. "
So if oxidise happens easily = more rate of flow = higher voltage = stronger electric field
But wouldn't also more rate of flow = more charges = higher current ?

 

[hutchphd]

an other post in this forum says "Basically, the battery's voltage depends on how easily your chosen chemicals oxidise or reduce. If redox reactions happen easily, then the voltage is higher. "
So if oxidise happens easily = more rate of flow = higher voltage = stronger electric field
But wouldn't also more rate of flow = more charges = higher current ?

The chemistry sets the voltage (electrochemical potential). The capacity to supply current at that voltage is set by the size of the battery (really the surface area of the internal plate/electrolyte interface). The electrical "model" is a perfect voltage source in series with a resistance (look this up if you need to ).

 

[rude man]

There are two E fields within a battery. One is electrostatic and points from + to -, the other is the source of emf and points in the opposite direction, i.e - to +.

(Positive) charges are impelled by the emf field from the cathode to the anode and simultaneously repelled by the electrostatic field.towards the anode. The two fields are equal and opposite in direction. There is no net E field within a battery.

Dr. Shankar of Yale, in his excellent intro physics course which you can follow on youtube, likens the procress to a ski lift: there is the pull on the rope pulling you up and gravity resisting the pull. He completes the analogy with a battery-resistor circuit.

 

[hutchphd]

There are two E fields within a battery. One is electrostatic and points from + to -, the other is the source of emf and points in the opposite direction, i.e - to +.

I would not describe the internal emf of a battery as being associated with "an electric field". The concept is not particularly useful and often confusing. There is a chemical process which supplies a fixed emf to the electrons. That's all you need to know.
If you are really interested in the gory details I suggest that you choose a particular type of battery (say lead acid) and learn everything you can about it. Then you can generalize that knowledge.

 

[Mister T]

thanks, i already know potential differences in an electric field and i want to know what "creates" this electric field between the copper and zinc plate in relation with oxidation and reduction of them at the electron level

The oxidation and reduction results in an excess of electrons on the zinc terminal and a deficiency of electrons on the copper terminal. The excess and deficiency are the source of, or as you put it create, the electric field.

 

[rude man]

I would not describe the internal emf of a battery as being associated with "an electric field".

The only thing that can move charge in longitudinal direction is an electric field.

There are other problems associated with the failure to ascribe an emf field in a battery, such as the fact that in a battery-resistor circuit the circulation of E is non-zero, which can only happen if there is a non-conservative E field somewhere around the circuit. Of course, that exists in the battery.

 

[rude man]

In general, an emf is generated when energy in a form other than electric is changed to electric. I admit to not being an expert in the chemistry inherent in the various forms of chemical batteries, but it's not germane.

Consider the formation of an emf from a time-varying magnetic field. Can you "explain" that? No, it's just an experimental fact discovered by Michael Faraday. What is needed is valid generalizations, in this case the inevitability of the formation of a non-conservative electric field whenever an emf is generated. This is observed in all known cases of emf generation and includes the photoelectric effect, the Seebeck effect, the piezoelectric effect etc. And also the electrochemical effect.

 

[gleem]

Consider the formation of an emf from a time-varying magnetic field. Can you "explain" that? No, it's just an experimental fact discovered by Michael Faraday.

Have you investigated the origin of the the Lorentz force?

 

[cele]

Well i will awnser my own question it's the surface charge distribution that creates the electric field For more information read matter and interactions 4th edition page 734

 

[hutchphd]

In general, an emf is generated when energy in a form other than electric is changed to electric. I admit to not being an expert in the chemistry inherent in the various forms of chemical batteries, but it's not germane.

It is certainly true that electromagnetic forces control every aspect of a common battery and that the work done on the electrons to provide them emf is all electromagnetic. But to talk about "an electric field" implies a well-described and static structure that does not comport with reality. The process is complicated and dynamic and not characterized by "an electric field". It involves many different electric fields over an electron's trajectory and so the statement should be discouraged.. What is well defined is the path integral for each electron which we call the potential.

 

[rude man]

The integral of the electric field generated by an emf (if you won't admit the existence of an emf E field in a battery you will surely do so in a Faraday setup?) is NOT the potential. A potential can be defined ONLY if the field is conservative. Basic math and basic physics..

If you have come up with a new force other than an electric field that can move charges in the direction of the field then you are in for a Nobel!

 

[rude man]

Have you investigated the origin of the the Lorentz force?

The Lorentz force is also nothing more than experimental fact: F = qv x B.
In fact, the Lorentz force is not a basis of any of Maxwell's equations whereas the Faraday law is (emf = - dΦ/dt is the basis for ∇ x E = - ∂B/∂t).

 

[hutchphd]

First please read what I said carefully..
The potential is called electrochemical because of the complexity. Every electron will see different E fields. Obviously a potential difference can be defined because that is how we normally define a battery.

If you have come up with a new force other than an electric field that can move charges in the direction of the field then you are in for a Nobel!

Now my turn to be snarky: ...gravity......
So show me a massless charged particle

 

[gleem]

The Lorentz force is also nothing more than experimental fact: F = qv x B.

Not so fast. Although Faraday's law was experimentally discovered it has a theoretical basis. In fact for the most general case of a circuit moving with a velocity of v in a time varying magnetic field B(t) it can be shown that

∇×E = -∂B/∂t + ∇×(v×B)

where E is determined in the coordinate system moving with velocity v relative that the coordinate system in which B is measures.

My statement about the origin of the Lorentz force was probably misleading. I just wanted to call your attention to the above equation.

The process is complicated and dynamic and not characterized by "an electric field". It involves many different electric fields over an electron's trajectory and so the statement should be discouraged

I agree.

 

[rude man]

Obviously a potential difference can be defined because that is how we normally define a battery.

A resistor also has potential difference. See, a resistor differs from a battery in that current flows from - to + but for the resistor it's + to -. EMF makes the difference.
A battery is defined by its emf, not its potential difference. A resistor has no emf across it.

...gravity......
So show me a massless charged particle

How many orders of magnitude is gravitational force typically less than electric? You'd have a hell of a time trying to move an electron with gravity ...

 

[hutchphd]

A resistor also has potential difference. See, a resistor differs from a battery in that current flows from - to + but for the resistor it's + to -. EMF makes the difference.
A battery is defined by its emf, not its potential difference. A resistor has no emf across it.How many orders of magnitude is gravitational force typically less than electric? You'd have a hell of a time trying to move an electron with gravity ...

Ever do the Millikan Oil drop experiment??

 

[rude man]

Ever do the Millikan Oil drop experiment??

Er, let me explain. The effect of gravity is on the oil, not the electron. The effect on the electron is due to an electric field.

 

[hutchphd]

No, let me explain (again)

It is certainly true that electromagnetic forces control every aspect of a common battery and that the work done on the electrons to provide them emf is all electromagnetic. But to talk about "an electric field" implies a well-described and static structure that does not comport with reality. The process is complicated and dynamic and not characterized by "an electric field". It involves many different electric fields over an electron's trajectory and so the statement should be discouraged.. What is well defined is the path integral for each electron which we call the potential.

Of course it is electrical. But you offered the Nobel.....how could I refuse?

 

[sophiecentaur]

I think the 'source' can be looked upon as what causes any chemical reaction, only in this case the charge imbalance is carried around by a wire. The electrolyte helps the process along by allowing ions to form at the electrode surfaces.

 

[gleem]

You'd have a hell of a time trying to move an electron with gravity ...

Although the gravitational force is infinitesimal compared to electrical forces none the less an electron is easily moved by gravity as the gravitational force on any mass is independent of the mass meaning in a vacuum all masses are accelerated at 9.8 m/sec². The force of gravity on an electron is equal to the force produced by a coulomb field of 5.6 x10^-11 V/m, the field produced by another electron 5.1 m away. So the electric fields produced at the atomic level of about 1 nm are huge.