Electron flow direction: Convention VS what's exactly happening

  • #51
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not sure i agree with you.

i was taught linear circuits from a generalized point of view, where you have across variables, and through variables. or as we would have called it at the time, linear network theory. (not to be confused with what most people would associate with networks now, computer networks). within this framework, you have elements that are sources (pretend there are only independent sources for now), and elements that are sinks. by convention, sources have positive across and through variables in the same direction, and on a sink, a positive through variable generates a positive across variable in the opposite direction. for linear electrical circuits, across variable is voltage, and through variable is current. this is conventional current. it is a consequence of a generalized version of a mathematical tool for analyzing linear networks.

now, it just so happened that the proton was assigned positive convention, and the electron negative, before this came about. if electrons had been labelled as positive, conventional current would be electron flow.

i couldn't find the across/through variable stuff on wikipedia (or rather i gave up while i was behind), but here's a couple of things to give you an idea of it.

http://www.mathworks.com/help/toolbox/physmod/simscape/ug/bq89sba-1.html#bq89sba-3 [Broken]
http://www.20sim.com/webhelp/modeling_tutorial/iconic_diagrams/acrossandthrough.htm
oh, and looks like google books lets you see it in one of Dorf's books
http://books.google.com/books?id=V-...ge&q=across variable through variable&f=false

i don't know, but i've been told, that the navy used to teach its techs electron flow. and that it made a lot more sense to do that when things ran on tubes.
 
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  • #52
dlgoff
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... but here's a couple of things to give you an idea of it.

http://www.mathworks.com/help/toolbox/physmod/simscape/ug/bq89sba-1.html#bq89sba-3 [Broken]...
I'm bookmarking this one.

Especially this part on "Direction of Variables":

...if an element is oriented from port A to port B, it implies that the Through variable (TV) is positive if it "flows" from A to B, and the Across variable is determined as AV = AVA – AVB, where AVA and AVB are the element node potentials or, in other words, the values of this Across variable at ports A and B, respectively.
ch1_var_direct1.gif


I love it. Thanks.
 
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  • #53
sophiecentaur
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The way that things are taught to Tekkies in the services is in order to get a short term result. It's not for Education and it's not an argument for doing it that way in School.

The Sign of Proton and Electron charge is a consequence of decisions made long before anyone knew they existed. There was no 'choice'.
 
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  • #54
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It's actually all a big mistake: electrons really do have a positive charge. However, when we talk about current, we still are correct because we also mistakenly believe we're made of matter when we're actually made of antimatter.

:biggrin:

I repeat my question "If many students express confusion, as many have, is this the fault of the students, the teacher or the syllabus?"
It's the universe's fault for being complicated.
 
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  • #55
Your post makes no sense to the reference of it's self
 
  • #56
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I dunno, it seems perfectly logical to me. Maybe i should elaborate that "when we talk about current" means "when we talk about actual current in real-world devices"
 
  • #57
309
1
It's actually all a big mistake: electrons really do have a positive charge. However, when we talk about current, we still are correct because we also mistakenly believe we're made of matter when we're actually made of antimatter.

:biggrin:


It's the universe's fault for being complicated.
Everything you know its wrong
Black is white
Up is down
And short is long
And everything you used to think was so important
Doesn't matter anymore, because the simple fact remains that
Everything you know is wrong
Just forget the words and sing along
All you need to understand is
Everything you know is wrong!

--"http://www.youtube.com/watch?v=EGC09B810Yk"" "Weird Al" Yankovic

I used to think I was a man, but now I'm not so sure. Would you double check for me? :shy:
 
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