Ohm's law

My know is just fine, everyone gets a turn.

Jamie

Win Hill? An online, "living", interactive(maybe?) version of AoE?

That's what network analyzers and poking tools are for - if the frequency shifts, you're poking the right thing.

If the bond ribbons blow at 3.31 GHz and 200W and nowhere else, you gots a parasitic resonance.

If the lump isn't there when the cover's off - box parasitic.

Kill 'em or move 'em to the free speech zone.

etc.

That has NOTHING to do with the idealized network theoretic components.

On Thu, 12 Nov 2015 17:29:37 -0500, M Philbrook Gave us:

Your know and your knob are f***ed, pi boy.

Not enough who learned anything about journalism, though.

Jim Thompson, wrote in :

Well, Mr Jim, I looked at that site, and I can see only somebody trying to share his insights with others. He may not tell the story the way you like it, and although he mentions 'complex' in the youtube video, he does not do those calculations, merely states that the current increases linear proportional with the voltage, in a given 'impedance', something that is true. Leaving phase shift and dissipation out if it.

I would not call him a troll, a troll is somebody who start thousands of off-topic subjects, holds the world record on commercial spamming on usenet by adding his company details to every off - and on topic posting.

And all I know is that the only spice simulation I ever tried from that troll is was his 'distortion free amplifier' and it was not distortion free, did not even run in LT spice.

So he who is a troll should maybe be a bit more lenient towards others who begin in this field.

Start Troll's commercial:

end troll's commercial

Hell you do not even know how to use google, need this group to find things from how to paint your garden furniture to how telling us proud you are shooting guns.

lol

(Sorry Jim but I had to laugh at that one! :)

I'm not sure Georg Ohm knew about quantum mechanics. :^)

George H.

Is Ohm's Law true for some fundamental reason? All real resistors seem to be nonlinear to some extent.

On Fri, 13 Nov 2015 11:32:02 -0800, John Larkin Gave us:

It describes a count of electrons passing a specific point in a conductor and how a resistive element interacts with the current level in that passage, and how said resistive element then "drops" a voltage across its entry and egress 'nodes'.

You need QM to describe the conductivity of metals. (A classical Drude model has too much scattering.) And then (I think) you need the drift velocity, (How much the E field changes the velocity of the carriers) to be a lot less than the Fermi velocity of the carriers. (The fermi velocity will be related to the fermi energy.. like 1/2 m v^2 but I don't know if you can always use the classical energy-velocity formula.) So, making things up now... If you have really high electric fields I think it will break down... (And now we'll wait for Dr. Hobbs)

George H.

On Fri, 13 Nov 2015 12:30:15 -0800 (PST), George Herold Gave us:

snip Larkin's retardation.

I like the idea of discussing "slow light" better.

Well, the wire will melt first.

But Ohm's Law isn't a law of nature, because it's never exactly true. One can get into real trouble, designing precision gear, by assuming that it is true.

Yeah, I'm not sure anything I said is true. At some point ohms law has to be about scattering. (Just to be clear I think we're talking about the linearity of the current with voltage, and not the temperature dependence of resistors... but maybe it's the temperature dependence you are thinking about?)

So once I have this QM model that only the electrons within ~kT of the Fermi edge are contributing to the motion, change. I then have a classical picture of electrons buzzing around and scattering off things inside the lattice. And as long as the added velocity doesn't change the energy much, then current goes as the E-field times some scattering time (length?) (I need a units check.)

Do resistors have voltage coefficients at constant temperature? (Voltage coef, that aren't just thermal effects.)

George H.

Most resistors have a non-thermal voltage coefficient, with an upward curve of current vs voltage (lower ohms at higher voltage.) Carbon and cermets are the worst, but thinfilm metal resistors do it too.

F=MA isn't true in the real world, either, but it's usually good enough. Ohm's Law is more of a definition of resistance than a "law of nature". If real resistors don't act ideally, well, do you expect them to?

When circuit elements are transformed into the frequency domain, it's true that there's proportionality rule analogous to Ohm's law. But it's only analogous. It is not Ohm's law.

Sylvia.

Thermal effect and nonlinearities are scattering/quantum/thermodynamics. Just about any isotropic material that passes current when a voltage imbalance is applied, ought to (by series/parallel construction and symmetry) be the same as a combination of smaller resistive chunks with scaled-down V, I... which eventually gets down to the one-dimensional point-equation of Ohm's law, * =- dV/dx where the constant is the material property of resistivity.

At the small-scale level, dV/dx is the only direction in the equation, and the constant has to be positive or energy isn't lost to heat. The material determines the constant. Things like diodes and Zener diodes don't have the isotropic condition, there are aligned layers and quantum mechanics that set a critical condition on dV/dx. Photoconductors aren't in thermal equilibrium, which rather adds to the confusion.