The resistance of a wire without a voltage bias

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Discussion Overview

The discussion revolves around the behavior of electrons in a wire without an applied voltage bias, specifically focusing on whether the collisions of rapidly moving electrons with atoms contribute to the warming of the wire. The scope includes conceptual reasoning and analogies related to thermal energy in systems.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that even without a voltage bias, the rapid movement of electrons (on the order of 10^5 m/s) leads to collisions with atoms, which could potentially warm the wire.
  • Others question the source of information regarding the speed of electrons and reference a specific physics textbook to support their claims about drift speeds and thermal motion.
  • A participant draws an analogy between free electrons in a metal and molecules in a gas, suggesting that without energy transfer, a system does not warm itself.
  • There is a discussion about whether thermal energy is preserved in equilibrium conditions, with some asserting that internal energy is conserved if no energy is transferred in or out.

Areas of Agreement / Disagreement

Participants express differing views on the implications of electron collisions on thermal energy and whether thermal energy can create more thermal energy. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants reference specific assumptions about thermal energy conservation and the behavior of electrons in thermal systems, but these assumptions are not universally accepted or clarified.

hokhani
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When a bias is applied to a wire, due to the resistance of a wire, the electrons colliding with the atoms make the wire warmer. However, we know that without any bias the electrons also move with very large velocity (of the order 10^5 m/s). How about the collision of these rapid electrons with atoms? Do these collisions warm the wire or not?
 
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hokhani said:
However, we know that without any bias the electrons also move with very large velocity (of the order 10^5 m/s).
where did you read that ?
 
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hokhani said:
When a bias is applied to a wire, due to the resistance of a wire, the electrons colliding with the atoms make the wire warmer. However, we know that without any bias the electrons also move with very large velocity (of the order 10^5 m/s). How about the collision of these rapid electrons with atoms? Do these collisions warm the wire or not?

With a bit of thought, you can answer your own question. Free electrons and atoms in a metal can be analogous to molecules in a gas. The molecules move and they collide. If you have a box of still air, does it warm itself? If not, why not? Where does the energy to move the molecules come from? Where does it go to?
 
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davenn said:
where did you read that ?
Please see Physics(2) (Electricity & Magnetism), Resnick, Halliday, Krane, Volume Three, Fifth edition, page 665, the left column.
The sentence is: "The drift speeds of electrons in typical materials are very small compared with the speed of the random thermal motions of electrons (typically 10^6 m/s)"
 
anorlunda said:
still
Thanks. Do you believe that in the equilibrium conditions, the thermal energy is preserved in the system?
 
hokhani said:
Thanks. Do you believe that in the equilibrium conditions, the thermal energy is preserved in the system?

It is just like any other thermal system if no energy is transferred in or out, the internal energy is conserved.

I said still only to exclude things like a vertex in the air.

Do you understand now? Your original question was asking if thermal energy creates thermal energy.
 
anorlunda said:
Do you understand now? Your original question was asking if thermal energy creates thermal energy.
Right, Many thanks.
 

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