| MadSci Network: Physics |
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… http://www.madsci.org/posts/archives/nov2000/973264612.Ph.r.html with an “r.html”, not a “q.html”. I think a little research about Joule heating on your part may help you 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… http://physics.about.com/cs/thermodynamic1/a/heaterresitance.htm Good luck in your future investigations! ---* D.r Ken Beck
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