Beating a dead horse

Discussion in 'General Electronics Chat' started by danuke, Dec 20, 2010.

  1. danuke

    Thread Starter New Member

    Dec 20, 2010
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    I did see a comment regarding current flow, conventional vs electron.
    It seems to always to boil down to Ben Franklin. Ok, that's fine, however, the electron was discovered about a hundred years later Old Ben did his thing. Now since then, it sure seems to me that there was plenty of time to get current flow theory right in the first place. That is, no need to even talk about surplus vs charge.

    I mean, it sure seems that science, engineering or what have you, wasted no time in saying oh, that the Earth orbits the Sun, and that is what we are gonna teach. So why can't electronics do the same? This is not brand new stuff after all; regardless of what is said. To my way of thinking, some academia somewhere just could not face reality and got the old way of thinking to stick.
     
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
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    It's all a matter that didn't come out until Physics was brought into the general light. Electrons go from - to + and they're all that actually move, the "holes" created do not move but are filled in by the next electron going in that direction.

    The thing is we got used to using the + as the top side of a schematic mainly because that has always been the usual power supply distribution notation.

    Think of it as you may, but the more positive a power supply is the more attraction it will have for moving the electrons from the source.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    Which is why our text book uses electron theory. We kept getting arguements about it in the Feedback and Corrections forum, so I wrote a quick explination and it was made a sticky.

    The real problem is it keeps being taught in school. Go figure.
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    The more I think about it they did the schematics that way because we has so many different potentials AND we were in the tube days where most everything was based upon positive potential with only a small amount of negative bias, much of which was generated with respect to the the cathode potential of the tubes.

    I do wish they'd teach simple tube technology as at least a simple chapter in the schools instead of "at one time" because there's a lot to be learned there. I need not expound on this.

    I'd still be building some thing with tubes if it hadn't become so hard to find good ones and everything associated but there are some rather impressive MOSFETS that sure make RF a lot easier given proper PC layout. A 2.4 GHz amp is still somewhat of a challenge but I've certainly got the antenna parts down.

    I've got an old X-band 10 GHz test oscillator down in the garage that, if I recall, varies the Klystron from 8.5 up to 10.5 on a complicated vernier dial calibrated in 100 KHz increments and puts out about a watt. With the right antenna and modulation input I could drive any police speed trap that set up near my shop nuts with it. Call me the devil but me and my partner at the time couldn't help but laughing when a car would drive by and they'd register it as going 120 when it was probably only going 35.

    A friend at college got into Gunn diodes and built something mobile that was extremely innovative, he could dial in the speed he wanted them to see and that's what they saw. That went on for a number of months until they caught on to how he was doing it and finally caught him in the act, confiscated his box and it wasn't long until radar jammers were outlawed. I have no idea if he was the first or just got the idea elsewhere but after he graduated he was grabbed by John Deere to develop sensors that could tell when a tractor tire was slipping and adjusted the differential to compensate.
     
  5. someonesdad

    Senior Member

    Jul 7, 2009
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    When I was a student in the 60's, we were required to go over to the EE department and take one EE course. My roommate and I wound up taking a network theory course; I wish I had taken something more practical, but the network theory course was good for learning some basic principles and the teacher was superb. Anyway, a key point driven in by the teacher was to show that for circuit analysis, it doesn't matter what direction you assume current flow. You'll get the right answers whether you use the positive convention or the negative convention. I remember the teacher also commenting on the fact that the two different conventions seem to upset different people in different ways. He encouraged us to get over any upset and get on with the task of applying the knowledge. It was good advice. In modern parlance, we'd say "Drop the stick and take five steps away from the horse." :p
     
  6. AlexR

    Well-Known Member

    Jan 16, 2008
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    I totally agree with someonesdad and can't understand why the hang-up with conventional current flow vs electron flow. Both views of the world have there place and either one if used consistently will give you the correct answer. Personally I use whichever suits the problem best.
    The trouble with using electron flow exclusively is that that the real world is set up around the conventional current model. Semiconductor symbols show the arrow in the direction of conventional flow, meters, batteries etc have +ve terminals red and -ve black so by implication current flows from high potential (+ve, red) to low (-ve, black).
    Just have a look here (http://www.allaboutcircuits.com/vol_1/chpt_10/2.html) at the Orwellian mental gymnastics that the author goes through to shoe-horn the electron flow model into what was clearly originally conventional current flow problem, even to the point of connecting a meter backward across a battery to "prove" that positive is negative. I just hope no-one tries that with an analogue meter!
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Everyone talks about semiconductor arrows being created for conventional flow. Personally I learned both electron flow and semiconductors pretty close to each other, and have never seen a discrepancy.

    As I've said in the sticky, there is a correct direction of flow. It explains a lot of phenomena that couldn't be explained otherwise. The reverse is not true. Given this basic fact why confuse the issue and teach the system that works in every case.
     
  8. AlexR

    Well-Known Member

    Jan 16, 2008
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    Because the real world is solidly tied to conventional current flow and unless the student can think in both modes he/she will have trouble as he/she advances. When I studied electronics many decades ago we were taught both electron flow and conventional current flow. I can't recall that is caused any great confusion or problems. Are today's students that much denser than we were that they can't handle both concepts at the same time? Surely that makes more sense than connecting voltmeters backwards across batteries in some vain attempt to prove that positive is really negative.
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    If you are working at the component level, you can pick one or the other and do well. As long as you do not try to mix concepts within a circuit.

    When it gets down to doping silicon, then it matters. Unless you are designing ICs, it doesn't really matter which way you label the current flowing, as long as you are consistent about it.
     
  10. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Anyone ever wonder why they label FETs with a drain and a source? Where is the source terminal usually connected?
     
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