How does electric current flow through a conductor

  • #36
AlphaLearner
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Finally came to a conclusion. There's nothing separate like an 'Insulator' and 'Dielectric'. Every insulator is dielectric. Every insulator has some degree of tolerance against electron flow no matter its state of matter is... That degree of tolerance is measured as volt/meter, Number of volts the current has between electrodes displaced by 1 meter. This even show smaller insulator requires some voltage to break through it and make current pass through it. The same insulator with larger length require much more larger voltage to pass through it . A cathode ray tube require over 10,000 volts to make electric current pass through gas over a few centimeters. But a lightning strike requires over 100 million volts to pass through a few meters of air. (Of course, gas in cathode ray tube is hydrogen and air is a mixture of gases so materials in both cases are different).
How could this be anywhere linked to resistivity in electron flow? Is it possible? Will a property like this even exist in conductors but of less/negligible value? Is this what the measure resistivity for them is?
 
  • #37
Drakkith
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How could this be anywhere linked to resistivity in electron flow? Is it possible? Will a property like this even exist in conductors but of less/negligible value? Is this what the measure resistivity for them is?

I'm not sure if you're asking about the dielectric properties of the conductor or the resistivity of the conductor.
 
  • #38
AlphaLearner
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I'm not sure if you're asking about the dielectric properties of the conductor or the resistivity of the conductor.
I am just asking will both have a link? Is resistivity is nothing but the possession of dielectric character even in a conductor? Or both are completely different?
 
  • #39
Drakkith
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I am just asking will both have a link? Is resistivity is nothing but the possession of dielectric character even in a conductor? Or both are completely different?

Resistivity and polarizability (which is essentially what determines how good of a dielectric a material is) are both properties of a material, but I don't know if they are linked to each other. I would think that the answer is no, but I don't have the necessary knowledge to give you anything more than a guess,
 
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  • #40
AlphaLearner
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All I know regarding resistivity of conductor is property of resisting flow of electrons and has various factors like area of cross - section, material of wire, temperature... But will what resists this flow of electrons is mainly the possession of partial dielectric character which depend on material of conductor is what struck in my mind for a while...
I am questioning regarding how far the conductivity of a good conductor is affected by this property.
Or diectric property has nothing to do with it... Anyone?
 
  • #41
UsableThought
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Is resistivity is nothing but the possession of dielectric character even in a conductor? Or both are completely different?
Resistivity and polarizability (which is essentially what determines how good of a dielectric a material is) are both properties of a material, but I don't know if they are linked to each other. I would think that the answer is no, but I don't have the necessary knowledge to give you anything more than a guess,
To the extent I am capable of saying anything sensible here, I agree with Drakkith. Essentially there are differences at the atomic & quantum level between materials that are good conductors, vs. good insulators; and this also applies to semiconductors. So it wouldn't seem safe to assume that a term useful for discussing insulators (e.g. dielectric) shares its meaning in some way with a wholly different term (e.g. resistivity) that is useful for discussing conductors. It's not a bad question to ask, however - especially if considered as an incentive to do more reading!

It is easy to find articles online that bring up this sort of thing - e.g. https://www.halbleiter.org/en/fundamentals/conductors-insulators-semiconductors/ - but to me this is the sort of question where nothing is going to replace some dedicated reading of textbooks that explain all of this thoroughly. Trying to learn it in bits & pieces doesn't seem like it will be profitable.
 
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  • #42
Drakkith
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I am questioning regarding how far the conductivity of a good conductor is affected by this property.
Or diectric property has nothing to do with it... Anyone?

Hmmm. I would think that good conductors usually don't make good dielectrics because, instead of storing energy by shifting polarized molecules around, most of the energy is expended moving electrons around. Insulators don't allow much current flow, so they typically make much better dielectrics than conductors.

Unfortunately that's more of a guess than anything else. I have nothing to back that up and I think we may have reached the limit of my knowledge in this area. :frown:
 
  • #43
AlphaLearner
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Hmm... surely! Will definitely go through a round and comeback here to conclude and verify.
 
  • #44
UsableThought
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Insulators don't allow much current flow, so they typically make much better dielectrics than conductors.

This was something Maxwell looked at when working up Faraday's research - I was just looking in a double biography of the two men & this particular point was mentioned in a passage where Maxwell is conceptualizing models of flux. It's over my head as to the exact meaning (I don't have the math to understand anything Maxwell did), but still interesting. From a passage on p. 160 of Faraday, Maxwell, and the Electromagnetic Field: How Two Men Revolutionized Physics, by Nancy Forbes and Basil Mahon:

In Maxwell's fluid model of the static electric field, substances like metals, in which electric currents could flow freely, took no part except that their surfaces could act as sources or sinks. Electric lines of force occurred in insulators - substances in which current did not flow. As Faraday had found, these substances varied in their ability to conduct electric lines of force - each had its own specific inductive capacity. For example, glass conducted electric lines of force more readily than wood.​

Etc.
 
  • #45
Sharad s
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The good question
The conduction of electricity through the conductor is a interesting phenomenon. Here the conductor's are those which allow the current to pass through them. ACC to chemistry the conductor's must have an single free electron in its outer most orbital thus when the energy is passed these electrons get ditached from the atom and has the negative charge over it. When these electrons come in contact with the positive charge due to change in potential of +ve & -ve particles these release the energy this is the electricity which we get. Electricity never flow from +ve to -ve due to low potential
 
  • #46
Drakkith
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ACC to chemistry the conductor's must have an single free electron in its outer most orbital thus when the energy is passed these electrons get ditached from the atom and has the negative charge over it. When these electrons come in contact with the positive charge due to change in potential of +ve & -ve particles these release the energy this is the electricity which we get.

The very best conductors happen to have a single electron in their outer shells (silver, copper, gold, and aluminum all have an electron configuration of s1), but the vast majority of conductors do not have a single outer valence electron. After aluminum, the next best metallic elemental conductor is calcium, which has an electron configuration of s2.

Also, note that the electrons are already detached from their atoms prior to any current flow. The metallic bonds that form between the atoms exist primarily because all of the atoms in the entire material are sharing their valence electrons with each other.
 
  • #47
Sharad s
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The resistivity of the material depends on all those factors it's true. The resistivity is also because of the nuclear charge acting on the free electron which is participating in the conduction of current. The increase in the temperature of the wire will provide the essential energy to the free electron to go away from the nucleus of an atom. The Next factor length and area of crossection due to the increase in the number of atoms the nuclear forces play an important role and thus the resistivity of the material increases.
If any queries contact my mail and id
 
  • #48
Drakkith
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The increase in the temperature of the wire will provide the essential energy to the free electron to go away from the nucleus of an atom.

A free electron is already free of its bond to any single atom. That's what "free" means.
 
  • #49
Sharad s
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A free electron is already free of its bond to any single atom. That's what "free" means.
The free electron mean the single electron in the orbital of the ultimate shell
 
  • #50
nasu
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No, it means that is in no specific atomic orbital, as Drakkith said. If you are more familiar with chemistry, think about a molecule. The bonding electrons are not in atomic orbitals but in molecular orbitals, which are extended over all the atoms in the molecule. The benzene molecule is an example of such de-localized electrons. A metal is like a huge molecule, with the binding "orbitals" extending over the whole metal. In metals there is no such thing as "detaching" the conduction electrons from the ionic cores. They are already as "detached" as they will be. The concentration of free electrons in metals is also independent of temperature, as they are all free at zero K.
In semiconductors you need some energy to promote electrons from the valence band to the conduction band. This energy is provided by thermal motion or/and absorption of light or maybe other processes. Maybe this is what you have in mind.
 
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  • #51
sophiecentaur
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The free electron mean the single electron in the orbital of the ultimate shell
But, in the solid state, it is not in any orbital. That energy state doesn't exist in the bulk material. Perhaps "would be in the orbital of the ultimate shell of an isolated atom" would be a way to describe it. But in an isolated atom the energy states of other electrons would actually be a bit different too.
 
  • #52
Sharad s
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But, in the solid state, it is not in any orbital. That energy state doesn't exist in the bulk material. Perhaps "would be in the orbital of the ultimate shell of an isolated atom" would be a way to describe it. But in an isolated atom the energy states of other electrons would actually be a bit different too.
In the molecules the nonbonding electrons are one ultimate molecular orbital the solid state is also a collection of molecules and thus these help in flow of current
 
  • #53
sophiecentaur
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In the molecules the nonbonding electrons are one ultimate molecular orbital the solid state is also a collection of molecules and thus these help in flow of current
I'm not sure that you describe metal structures in terms of 'Molecules' isn't is all just one big lattice of ions? Are you saying that the next highest 'orbital' contributes to electrical conduction? Is that always or just in some rare instances?
Edit: If you are right then wouldn't the strength of a metal be affected by a heavy current flowing through it? i.e. the bonding would change.
 
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  • #54
Joseph M. Zias
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This has been a very discussed topic in recent years. Many articles have appeared over the past 15 years or so but there were some way back in the early 60's.
Here is a bibliography of some of those papers:

W.G.V. Rosser. “What makes an electric current flow“, Am. J. Phys. 31 , 884-885 (1963)

Ian Michael Sefton, “Understanding Electricity and Circuits What the Texts Books Don’t Tell You”, Science Teachers Workshop, 2002, Sydney, Australia

J. D. Kraus, Electromagnetics, 2nd ed. (McGraw-Hill, 1973) p 416-418

J. D. Kraus, Electromagnetics, 4th ed. (McGraw-Hill, 1992) p 577-580

W. Beaty, “In a simple circuit, where does the energy flow?”, Science Hobbyist,
http://amasci.com/elect/poynt/poynt.html (12, 2000)

R. W. Chabay and B. A. Sherwood, Matter & Interactions, 4th ed. (Wiley,
New York, 2015).

R. W. Chabay and B. A. Sherwood, “A unified treatment of eletrostatics
and circuits” (2006).

3J. D. Jackson, “Surface charges on circuit wires and resistors play three
roles,” Am. J. Phys. 64, 855–870 (1996).

M. A. Heald, “Electric fields and charges in elementary circuits,” Am. J.
Phys. 52, 522–526 (1984).

N. W. Preyer, “Surface charges and fields of simple circuits,” Am. J. Phys.
68, 1002–1006 (2000).

I. Galili and E. Goihbarg, “Energy transfer in electrical circuits: A qualitative
account,” Am. J. Phys. 73, 141–144 (2005).

M. K. Harbola, “Energy flow from a battery to other circuit elements: Role
of surface charges,” Am. J. Phys. 78, 1203–1206 (2010).

A.K.T. Assis and J.A. Hernandes, The Electric Force of a Current, (C. Roy Keys, Inc. Montreal, Quebec) 2007 (ISBN: 978-0-9732911-5-5)

Rainer Muller, “A semiquantitative treatment of surface charges in DC circuits” Am. J. Phys. 80,
(9), Sept. 2012.
 
  • #55
nasu
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In the molecules the nonbonding electrons are one ultimate molecular orbital the solid state is also a collection of molecules and thus these help in flow of current
Not in metals. There is a big difference in properties between molecular crystals (which indeed are a collection of molecules) and metallic crystals. Metals cannot be described as a collection of molecules, this is the whole point of introducing a new category (metallic crystals).

Also, ionic crystals are not really a collection of molecules. There is no meaningful way to say that a specific Na+ ion forms a specific NaCl molecule with any of the 6 Cl- nearest neighbors.
 
  • #56
Sharad s
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In the molecules the nonbonding electrons are one ultimate molecular orbital the solid state is also a collection of molecules and thus these help in flow of current
And the excitedstate of theS
In the molecules the nonbonding electrons are one ultimate molecular orbital the solid state is also a collection of molecules and thus these help in flow of current[/QUOTE
The flow of electricity is based on the exited state of the atom and also the lattice design of the solid
 
  • #57
AlphaLearner
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as they are all free at zero K
Are you sure about this? Then why metals contracting is not exactly because of just the lattice which has positive ions come closer but as you have said that even these positive ions would split out in absence of electrons so they even hold these at a place. I mean, even electrons start losing energy, fall to ground state in their respective atoms, begins to stick to nucleus of atom and overally such 'Free electron' count must also fall and at 0K, the overall number of free electrons should be almost negliglible (I don't say there won't be even a single electron unless it is some ideal material which obeys such change) then even conductivity should also fall. Till what extent can this be current guys?
 
  • #58
nasu
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I am not sure I understand what you are trying to say.
Of course zero K is a state that cannot be reached in practice but you can get infinitesimally close to it. And theoretically, the ground state of the electrons at zero K is with electrons in conduction band free. This is the ground state. There is nowhere to fall.
These thing are rally basic things, described in any introductory solid state textbook. The number of free electrons does not decrease at low temperature. The resistivity of metals actually decreases at low temperatures, as the scattering by phonons is reduced while the number of carriers does not change.

I don't understand how do you think that thermal expansion is relevant for the free electrons.

What is the point to try so hard to force a model which is not suited when you can just learn about it quite easily? There are many books available online.
 
  • #59
AlphaLearner
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Summarizing what I actually meant to say in #57 since what I wanted to express is not clear:

Now after reading what I wrote carefully, I thought of expressing contraction of metals will lessen the space, make structure more condensed, making free electrons trapped in latice causing problems for free electrons to flow, then I wanted to state that even since electrons lose energy from their ultimate energy level required for them to be free from that atom, electrons get closer to nucleus and due to nuclear charge on electrons, they show resistance to move from atom and went on... Finally wanted to say that there can't be 'Free electrons' to flow at 0K making conductivity of a materal almost negligible considering those above 2 main points. My main intention is to oppose that there can be 'Free electrons' at 0K in a conductor. Till what extent that electrons are still free to flow at 0K? No matter whether it is practical to create such a condition or not... Atleast in theory, is it possible?
 
  • #60
AlphaLearner
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There are many books available online.
I understand.
 
  • #61
nasu
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Summarizing what I actually meant to say in #57 since what I wanted to express is not clear:

Till what extent that electrons are still free to flow at 0K? No matter whether it is practical to create such a condition or not... Atleast in theory, is it possible?
I thought I already answered this (post 58).
But you don't have to take my word, just read some of the books.
Or maybe start with some quantum mechanics. The behavior of electrons in metals is not described by classical mechanics at all (the classical predictions are order of magnitude off). See Drude model versus Sommerfeld model.
The distance between atoms in the lattice is not really relevant for the mean free path of electrons. Actualy the mean free path increases dramatically at low temperatures. It can reach millimeters or even centimeters for very pure samples. This behavior cannot be understood in terms of classical collisions between electrons and atoms in the lattice.
 
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  • #62
AlphaLearner
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Or maybe start with some quantum mechanics. The behavior of electrons in metals is not described by classical mechanics at all (the classical predictions are order of magnitude off). See Drude model versus Sommerfeld model.
The distance between atoms in the lattice is not really relevant for the mean free path of electrons. Actualy the mean free path increases dramatically at low temperatures. It can reach millimeters or even centimeters for very pure samples. This behavior cannot be understood in terms of classical collisions between electrons and atoms in the lattice.
Thank's for your reply, I didnt notice your post yet it maybe marked away from green.
 
  • #63
Drakkith
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Summarizing what I actually meant to say in #57 since what I wanted to express is not clear:

Now after reading what I wrote carefully, I thought of expressing contraction of metals will lessen the space, make structure more condensed, making free electrons trapped in latice causing problems for free electrons to flow, then I wanted to state that even since electrons lose energy from their ultimate energy level required for them to be free from that atom, electrons get closer to nucleus and due to nuclear charge on electrons, they show resistance to move from atom and went on... Finally wanted to say that there can't be 'Free electrons' to flow at 0K making conductivity of a materal almost negligible considering those above 2 main points. My main intention is to oppose that there can be 'Free electrons' at 0K in a conductor. Till what extent that electrons are still free to flow at 0K? No matter whether it is practical to create such a condition or not... Atleast in theory, is it possible?

Even at zero kelvin there are still huge numbers of electrons in the conduction band of a metallic conductor (not in semiconductors though). Current actually flows better at extremely low temperatures in a metallic conductor than it does at room temperature, as nasu said in post #58. In fact, at temperatures near 0 K metals often become superconductive. Electrons are never trapped between ions in the lattice. They just don't work that way.

I'd also like to reiterate that you cannot think of conduction in terms of classical particles. Electrons are not hard, spherical balls that move through a material in set paths and bounce off of things like pinballs in a pinball machine. They are quantum particles that behave in non-intuitive ways.
 
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