Talk:Joule's laws

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Citations

Why does the section relating Ohm's law to Joule's law need citation? These are universally-known facts of electricity and physics, particularly P=V*I (power dissipated is equal to the voltage drop across a resistive component multiplied by the current flowing through the component). —Preceding unsigned comment added by 65.112.197.16 (talk) 01:04, 18 July 2008 (UTC)

As it turns out, the section was pretty much nonsense, just a bunch of algebra that didn't say what the underlying physical assumptions or constraints on applicability were. I replace it all with well-sourced stuff that actually explains the relationship, which in fact depends on three things: (1) the circuit is resistive; (2) the notion of electrical potential to explain electrical energy as charge times potential difference (or power as current times potential difference); and (3) conservation of energy, or equivalence of electrical work applied to heat dissipated. This is not explained at all well in a lot of modern sources that just want you to understand how to manipulate formulas, but in the other sources were they were working it out and trying to explain it, there's a wealth of good info.

Anyway, the general answer as to why something needs to cite sources is that it's hard to see how to improve it when you don't see where it's coming from. When something is well known, it should be easy to source, but if it's distorted folk lore, maybe it needs to be made verifiable by working it closer to sources. Dicklyon (talk) 22:06, 28 February 2009 (UTC)

What exactly is the joule effect?

In Wikipedia's article Current density, a (grammatically very messy) sentence mentions the "joule effect". So I entered "joule effect" into Wikipedia and it redirected me to Magnetostriction. Nowhere on the Magnetostriction page does it talk about the "joule effect", so I went looking further. The Joule's laws article states, "Joule's first law, also known as the Joule effect, is a physical law expressing the relationship between the heat generated by the current flowing through a conductor." This sounds like a very different principle from Magnetostriction to me. Other sources provide similar and differing definitions:

• Dictionary.com: Joule effect: the generation of heat by the passage of electricity through a resistance.
• Answers.com: Joule effect: The heating effect produced by the flow of current through a resistance.
• nasa.gov: Magnetostrictive Materials were discovered in the 1840s by James Prescott Joule, when he noticed that iron changed length in response to changes in magnetism and named the phenomenon the Joule Effect.

Can someone clarify how the "Joule effect" should be defined, and to what article on Wikipedia it should link? Wildbear (talk) 05:44, 17 July 2009 (UTC)

Books show at least two very different joule effects; electrical heating and one about stretched rubber bands that may be sort of related to the magnetostrictive one mentioned above. Probably we need a Joule effect article where we can talk about Joule and his eponymous effects. Dicklyon (talk) 05:50, 17 July 2009 (UTC)

I agree that a Joule effect article would be worthwhile, since it appears that the issue is complex enough that some technical and historical background on the various "Joule effects" would help to clarify the issue. If not a new article, then there should at least be a disambiguation page for Joule effect (resistive heating), Joule effect (Magnetostriction), Joule effect (gas expansion), Joule effect (rubber contraction), and any other Joule effects that I'm overlooking at the moment. I think an article would be preferable over disambiguation for this topic, and I'm willing to help work on it. Wildbear (talk) 02:54, 18 July 2009 (UTC)

Joule effect article created. Wildbear (talk) 08:27, 19 July 2009 (UTC)