Photons and electrons and electricity.

[Katysei]

A) I want to understand electricity in terms of quantum theory.
as I understand photons are the carriers of EM energy so
how do photons trasfer energy from electric company or battery through a wire.
and the connection to electron movement (do electrons from one atom bum into another electron in
another atom)
how is it different in cases AC and DC what is the directionality of photons and electrons.

B) current in wire causes heat, so what exactly causes it,in cases of good conductor and bad
conductor.

 

[ZapperZ]

A) I want to understand electricity in terms of quantum theory.
as I understand photons are the carriers of EM energy so
how do photons trasfer energy from electric company or battery through a wire.
and the connection to electron movement (do electrons from one atom bum into another electron in
another atom)
how is it different in cases AC and DC what is the directionality of photons and electrons.

B) current in wire causes heat, so what exactly causes it,in cases of good conductor and bad
conductor.

You DO know that such a topic covers whole chapters of books on Solid State Physics, don't you?

Maybe I can give you a simpler start. If you wish, you can look up the Drude Model. This might be an easier way to introduce you to charge transport in solids. Try to understand that first, and come back and ask questions here if there's something you don't understand.

Keep in mind that when atoms form a solid, they lose a lot of their individual characteristics. The energy levels that are typical for an atom is now gone (at least at the low energy range), and all the atoms collectively form "bands" of energy. That's why you have the conduction band and the valence band, and why we have energy gaps in semiconductors/insulators.

Zz.

 

[Naty1]

resistance heating...

introductory description here:


http://en.wikipedia.org/wiki/Joule_heating

 

[mcodesmart]

how do photons trasfer energy from electric company or battery through a wire.

Electrons transfer energy through a wire.

do electrons from one atom bum into another electron in
another atom

Absolutely. This is called electron scattering.

 

[Katysei]

You DO know that such a topic covers whole chapters of books on Solid State Physics, don't you?

Maybe I can give you a simpler start. If you wish, you can look up the Drude Model. This might be an easier way to introduce you to charge transport in solids. Try to understand that first, and come back and ask questions here if there's something you don't understand.

Keep in mind that when atoms form a solid, they lose a lot of their individual characteristics. The energy levels that are typical for an atom is now gone (at least at the low energy range), and all the atoms collectively form "bands" of energy. That's why you have the conduction band and the valence band, and why we have energy gaps in semiconductors/insulators.

Zz.

I was not aware of that.
I wiil read what ou directed me, does solid state cover electric transfer via lighting through air to the ground ?
I also thought of some high level regarding trsnfer/exchange of of photons to get general picture or I'll just stick to what you directed me?

thankx a lot
I have a lot of study to cover:)

 

[chill_factor]

I was not aware of that.
I wiil read what ou directed me, does solid state cover electric transfer via lighting through air to the ground ?
I also thought of some high level regarding trsnfer/exchange of of photons to get general picture or I'll just stick to what you directed me?

thankx a lot
I have a lot of study to cover:)

no. air is not a solid.

 

[Katysei]

Electrons transfer energy through a wire.



Absolutely. This is called electron scattering.

thankx for the reply.
I want to know how energy transfer is done through photon even when no wire
like in tesla coil or lightning.

 

[Katysei]

soilid, air, or fluid.

no. air is not a solid.

whether ions flow in liquid or lightning in the air or electrons in a solid wire.
I want to know how EM energy/photons are transferred
the big picture and reference to details(solid state already got)
thankx.

 

[Crazymechanic]

lightning is just a name we have given to a rapid electric breakdown of air it doesn't flow.The ions do yes.

Well quite honestly I think for starters you are asking very complicated questions which hardcore scientists themselves don't even know all the time.

Speaking about the flow of electricity there are two main things, one is the flow of charge , which is the actual flow of electrons at a given point and measures in Amperes.This is called current and it is responsible for the work that is done by electricity when it flows through a circuit.

Then there is voltage written as V and V describes the potential difference between two points.
Like rub your clothes against your hair and the hair and clothes will be set at a higher potential than ground so charge will be accumulated and once you will provide a path for it to flow a simple circuit will be formed and the potential difference will be lost due to charge flowing from the point of highest potential to the one of lowest.

Now if you wonder why electricity moves so fast and why actual electrons move so slow then your mentioned photons come into play.The actual electrons move slowly but once one of them is excited(current applied to a wire) it emits a photon which travels a the speed of light to hit the next electron and excite it so that it could move on to get the next one.Ofcourse there are billions of these interactions in a EM field and Em field itself propagates at c in vacuum and close to c in typical mediums like air around us.
This is the reason why when you listen to radio you here the news of today rather than the ones of yesterday.

 

[Katysei]

lightning is just a name we have given to a rapid electric breakdown of air it doesn't flow.The ions do yes.

Well quite honestly I think for starters you are asking very complicated questions which hardcore scientists themselves don't even know all the time.

Speaking about the flow of electricity there are two main things, one is the flow of charge , which is the actual flow of electrons at a given point and measures in Amperes.This is called current and it is responsible for the work that is done by electricity when it flows through a circuit.

Then there is voltage written as V and V describes the potential difference between two points.
Like rub your clothes against your hair and the hair and clothes will be set at a higher potential than ground so charge will be accumulated and once you will provide a path for it to flow a simple circuit will be formed and the potential difference will be lost due to charge flowing from the point of highest potential to the one of lowest.

Now if you wonder why electricity moves so fast and why actual electrons move so slow then your mentioned photons come into play.The actual electrons move slowly but once one of them is excited(current applied to a wire) it emits a photon which travels a the speed of light to hit the next electron and excite it so that it could move on to get the next one.Ofcourse there are billions of these interactions in a EM field and Em field itself propagates at c in vacuum and close to c in typical mediums like air around us.
This is the reason why when you listen to radio you here the news of today rather than the ones of yesterday.

thankx a lot I'm beggining to undestand.
last question if you may,
why photons seem to have ( I think) a strait directionality whether electrons flow in one direction (DC), or changing direction(AC) , eventualy we get them at home from the electric company.
( I would expect photons to change direction with the current direction.

 

[Katysei]

resistance heating...

introductory description here:


http://en.wikipedia.org/wiki/Joule_heating

thankx a lot naty.

 

[Naty1]

I want to know how energy transfer is done through photon even when no wire
like in tesla coil or lightning.

http://en.wikipedia.org/wiki/Lightning

A typical cloud to ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3 mi). The actual discharge is the final stage of a very complex process.

The voltage [electrical potential] build up causing ions [charged particle] to form and these are able to conduct electricity...it's a type of 'insulation breakdown'...

Once a conductive channel bridges the air between the negative charges in the cloud and the positive surface charges below, the flood gates are opened, and a massive electrical discharge follows.

The massive flow of electrical current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically-conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 50,000 K, causing it to brilliantly radiate with a blue-white color. Once the electrical current stops flowing, the channel cools and dissipates over 10's or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to explosively expand, producing a powerful shock wave that is heard as thunder.

Separately, you may find a bit of reading about plasma of interest:

http://en.wikipedia.org/wiki/Plasma_(physics )

The presence of a non-negligible number of charge carriers makes the plasma electrically conductive so that it responds strongly to electromagnetic fields. Plasma, therefore, has properties quite unlike those of solids, liquids, or gases and is considered a distinct state of matter.

The first part is true; the second part is true, but in my opinion are rather unrelated. A plasma is not a unique fourth state of matter because it is electrically charged: if that were true, semiconductors would also be classified as a 'plasma'...and electrons as well...Regarding current in a wire:

Crazymechanic posts:

..The actual electrons move slowly but once one of them is excited(current applied to a wire) it emits a photon which travels a the speed of light to hit the next electron and excite it so that it could move on to get the next one.Ofcourse there are billions of these interactions in a EM field and Em field itself propagates at c in vacuum and close to c in typical mediums like air around us.

I've never seen such a description involving photon emission. I don't believe photon emission is required. [Edit: I take that back...it's a quantum field theory perspective...It's not required in a classical discussion with fields and electrons.]

An easy way to visualize electron flow is like cars getting on a highway...when it is crowded [lots of conductors] one car can't get on here until all the cars move along there. Likewise, electrons repel each other and are pushed along by a potential. Equivalently, you can say the electric field moves all the free electrons along equally. The flow of ions, say in an electrolyte in battery or in salt sea water [electrolysis or galvanic corrosion] move along in like manner...no emission of photons is required there either. The field effects move close to the speed of light, but the electrons in a conductor move at a much slower DRIFT velocity.

Dr Zoidberg has some good insights here:

https://www.physicsforums.com/showthread.php?t=683365&highlight=electric+current+flowFor some views on quantum mechanics and electricity:
http://en.wikipedia.org/wiki/Semiconductor

 

[Crazymechanic]

"""why photons seem to have ( I think) a strait directionality whether electrons flow in one direction (DC), or changing direction(AC) , eventualy we get them at home from the electric company."""

I'm sorry for taking this to deep , by the way you don't know where photons travel , only when you measure one you can say something about it.
Also the electrons in your home wall socket do not come from the power company they actually have been there all the time in your wire.
Especially considering AC the net drift of electrons is zero because they oscillate back and forth with the frequency would it be 50 or 60 hz depending on the country you live in.
So actually the electrons you get in your house have been there all the time in the circuit boards , cables and all other conductors attached to the wall socket.You just can't use them unless they flow in a flow of electrons which they do because current is applied to the cable at the power station all the way to your house.