### Re: specifically, how do you obtain heat from the electric current?

Date: Tue Oct 26 18:10:17 2004
Posted By: Kenneth Beck, Senior Research Scientist, Chemistry and Physics of Complex Systems, Pacific Northwest National Laboratory
Area of science: Physics
ID: 1098387411.Ph
Message:
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Dear Pavel,

You know my fellow scientists will sometimes remark in a friendly, joking
way (and only to one another) that a little science can be a dangerous
thing.  I see in your question alot of thought and a desire to understand
the physical process known as Ohmic or Joule heating. But it’s also
riddled with a lot of labels and buzz-words (“color charge”?!) which will
only confuse rather than clarify.

Joule discovered the process of resistive heating in the 1840’s after Ohm
published his famous equation. Joule’s law is easily stated in terms of
Ohm’s law as,

Q = Pt = I^2Rt

where Q is the heat generated in time, t, I is the current, and R is the
resistance (P, as you probably guessed, is the power).

I’ve read over the earlier response from November, 2000.  The correct
URL, by the way, is…

with an “r.html”, not a “q.html”.

understand the process much better. But, I will answer you questions as
stated in “Facts/premises” 1-4:

(1) If we are only considering Joule heating, electron collisions
determines the amount of atomic vibrations within a material.
Collisions of electrons set in motion by the applied electric field with
(still) bound electrons in the material. This motion is rather fast
compared to the motion of nuclei within the atoms.  They will be slower
to respond.  But when they respond to the momentum of multiple electron
collisions, they will excite the structure of the material
vibrationally.  This can be measured as a rise in temperature.

(2) Well, no.  This is not a fact or a valid premise.  Free electrons do
concern us.  They are set in motion by an applied field and are in motion
until they collide/  They transfer their momentum and energy to bound
electrons of the material.

(3)  Let’s be specific.  We’re talking about Joule heating, not
ionization or photoluminescence (“releasing a photon”).  I know you’re
trying to understand all this in terms of the extremely ancient 20th
Century notion - the Bohr atomic model.   The reason electrons occupy
different states in an atom is predominantly because of their electronic
energy, in addition to their, generally, smaller angular ( orbital and
spin) energy.

(4) Again, we’re talking about Joule heating, not thermonuclear
transformation of mass and energy (e=mc2). Electrons in a material are
set in motion by an applied electric field.  They collide with (still)
bound electrons, setting atoms in motion.  This motion we measure as a
temperature rise and generated heat.  Here’s a reference for you…
http://encyclopedia.thefreedictionary.com/Joule+heating

and another with worked example and further references to heating an
electricity…

Good luck in your future investigations!

---* D.r Ken Beck

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