How does electric current flow through a conductor

  • #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
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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
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
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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
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 dont say there wont 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
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 cant 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?
 
  • #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
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 cant 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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