That's how it's explained:
That's how it's explained:
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Where are the coulombs and joules in that drawing?
The best way to explain three new concepts is not by adding two more new concepts.
Drilling down to bedrock is not always the best way to learn something. As a kid, the current convention always bothered me, because I knew current was a flow of electrons, and electrons went the other way. Did current reflect a hole-centric way of looking at things?
But then I realized electrons were irrelevant to my study of current flow. They're important to a deeper understanding of electronics, but if you're not operating at that level they just get in the way.
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I don't think you sufficiently understand voltage. Explain to me the difference between the abvolt and the statvolt, to prove me wrong.
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You don't start by teaching them about the leap second if you want them to learn about the big hand and the little hand. Similarly they don't need to know about how the earth wobbles on its access to know when it's a quarter to five.
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Don't make up stuff, but don't teach them more than they can absorb. If some kid asks how an airplane flies, you don't need to start your explanation by teaching him tensor mathematics.
On Mon, 23 Jan 2012 21:23:10 -0500, TonyS wrote (in article ):
I love it :-)
-- Nelson
On Tue, 24 Jan 2012 03:23:58 -0500, spamtrap1888 wrote (in article ):
[Snip]I still find myself occasionally getting momentarily hung up on this... and I have Master's Degrees in Electrical Engineering and Physics :-) I have always found "holes" counterintuitive. It's too bad the conventions didn't evolve so that they were consistent with the underlying physics. It's as if we defined the basic unit of heat as the "friggie" so that when a body heated up, we would say it lost so many friggies.
-- Nelson
No. See below.
Positive and negative, as you point out, are misnamed. This is supposedly the fault of B. Franklin, who said that electrical particles flowed from an source with an excess to a sink with fewer -- which is basically correct. He called the excess side "positive", not knowing that the charge of the electrical particles would eventually be called "negative".
BY CONVENTION, current flows from positive to negative. This has never much bothered me, nor has hole flow. (A hole is a place in the lattice where an electron "should" be.)
Now, if someone could explain exactly how -- on a quantum level -- junction transistors work -- I would be delighted. I've yet to find a book that makes it clear. (FETs are easy.)
They're just different units. Convert by multiplying by a constant. That's all. It's like using the bell instead of the decibel or microns instead of angstroms. That's not a big deal.
Which has nothing to do with avoiding teaching them something that's wrong.
Resistance is not a fundamental quantity. It's nothing but the ratio of voltage and current, and only when measured in the absence of other factors which are fundamental, so it's not something you should refer to when explaining voltage.
The last sentence in the cited web page could simply be deleted and nothing would be lost. I'm baffled why you think it's so important to include it.
-- Reply in group, but if emailing add one more zero, and remove the last word.
You can never reach bedrock.
So you just think of current as an abstraction. You don't think about holes. You didn't need to learn (at first) about holes. But you also didn't need to learn a lie about positive particles. It can just be left as an abstraction. So can voltage.
-- Reply in group, but if emailing add one more zero, and remove the last word.
Coulombs and joules are in the other drawing, in the web page in question. They were included without naming them in an abstract and intuitive way. Then the author went off in the wrong direction when he should have just left it as an abstraction.
-- Reply in group, but if emailing add one more zero, and remove the last word.
=A0Adults assume
provide
Do not be too quick to judge on that. Mostly learning it wrong first is the real stumbling block rather than abstraction itself. Learning formal abstraction is a different issue, and needs to be treated as such.
explained:
What happened was merely an incorrect A|B choice long before there was anything enough information to decide correctly. But it has been = embedded in the ASSumptions for hundreds of years and there is no reasonable way = of correcting it. Not that electrons move in conductors at anything like light speed.
?-)
=A0That's
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That's like saying a pound is a unit of mass. Try again.
g.
frs
What do you mean by fundamental property? Resistance (more precisely, resistivity) is a materials property, as is potential difference. If I make a cell (defining the voltage) and apply it to a hunk of material (geometry plus a property of the material), that defines the current that flows through the material.
On Wed, 25 Jan 2012 01:20:52 -0500, spamtrap1888 wrote (in article ):
I could swear I recall deriving resistivity from the fundamental properties of the material in question such as it's crystalline structure, electron scattering cross-section, temperature, etc. Quantum Thermodynamics or something. It was a very long time ago :-)
Since neither "voltage" nor "current" are inherent properties of materials, resistivity would seem, to me at least, be the more "fundamental" property.
As an analogy, you can define mass as the ratio of applied force to acceleration, but I think most people would say that mass continues to exist in the absence of force and acceleration and hence is a fundamental property.
-- Nelson
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