From this thread: http://forums.bit-tech.net/showthread.php?t=89113 Do you think Conventional Flow or Electron Flow is the proper idea when designing electronic circuits? More explanation: http://www.allaboutcircuits.com/vol_1/chpt_1/7.html ------------------ My opinion: If scientists would not have assumed positive flow in the first place, and used the real electron flow, circuits today would be much more efficient.
People are used to thinking about "positive charge flowing round a circuit" so it makes some sense to keep it that way, annoying though it may be. I was thinking just the other day about how different things would be if that 50/50 chance of picking positive charge going one way or the other was made differently all those years ago before knowledge of electrons and all that. I agree that we'd probably have far more efficient circuits than we do at the moment, not to mention the fact that because electrons would be thought of as "positive", positrons would be called "negatrons". How cool is that?
It absolutely does not matter, unless you have a surface that emits electrons in your circuit, like the cathode in a vacuum tube (it always emits electrons). Just to stay with the convention assume that current flows from + to - outside a power source and from - to + inside it.
Electricity was discovered and its properties and units defined several centuries before electrons were known to exist (if they do, nobody's seen one) so any argument now is pointless. Symbols for active components such as diodes and transistors have arrow symbols that show how conventional current can flow - positive to negative, high voltage to lower. The logical way - given the scientific knowledge of the early 19th Century. Anybody interested in designing and building simple electronic circuits only needs to know what components can do practically and the maths formulas that apply. He doesn't need to know how they do it at the sub-atomic level, any more than he needs to know his LED is made from Gallium Aluminum Arsenide. Colour and forward voltage/current rating will do. And anybody studying the subject any deeper will find the theory of charge flow covered in the first few pages of his textbook. Now, why do you drive on the wrong side of the road?
i agree with cpemma on this one -- it is much easier to understand way circuits are drawn out when going with the convention. for example, as people draw diagrams, they are going to do things like put Vcc at the top (the "source") and Vdd or Gnd ("drain") at the bottom because things fall from top to bottom in the world we CAN see. unless you are working with ic's on a transistor to transistor level, and dealing with things like silicon doping, its not necessary to go against convention as there is no obvious benefit
Very nicely put, cpemma. Electricity is the flow of electrons through a conductor. Electrons are negatively charged. The actaul flow of electrons is opposite to what conventional current flow is taught. But this is how it works: As an electron 'hops' from one atom to another (in the direction towards a positive charge), it leaves behind a 'hole'. That atom is more positively charged without that electron, so it steals an electron from its neighbor atom. This keeps going until you have this cascade of electrons flowing through your conductor. Even though there is no actual physical particle that makes up the 'hole', it is considered a flow of positive charge. See, here is why this gets confused in the first place: People often try to use gravity (water flow) as an analogy to electric theory. This is sooo wrong. Gravity is positional/directional , where as electricity is pure potential. In no way does circuit theory constrain itself to the flow of electrons. It is based upon potential (the difference of voltage between two points). These two voltages could be negative, or they could both be positive. It does not matter. What matters is which has a higher potential to the other. This comes down to the arguement differences between engineers and physicists. The physicist: This is WHY it works. The engineer: This is HOW to make it work.
I personally think the gravity/fluid analogy is quite a good one for most electrical circuits you could encounter. Think about the terms: Flow, Potential, Circuit (circulation), Ground. Well this is all relative. Usually you would define the lowest potential in a circuit as zero volts, just as you'd define the ground, or the bottom of a shaft as zero gravitational potential. There's no "universal zero voltage" just as there's no "universal gravitational centre" (you could argue that it's the gravitational centre of the universe, but it'd be a stretch, especially considering the kinds of places we normally consider to be "the ground")
But most of us are just happy to be fitters, who want to know how to put it together from the engineer's drawing of the physicist's theory. (And gas fitters and plumbers get paid more moolah than most engineers)
err, im not sure how it works in the EU, but in the states, most collages guarantee a (30-50k per year) job as soon as you graduate with a CS/CE degree... most plumbers are lucky to make 50k after 10 years of experence...
Not sure where in the US you are, but in the NE, if a plumber is good and hustles (in the always working sense of the word), he can easily make that. That's been my experience, I used to work in plumbing supply for a good bit. A plumber friend of mine just bought a house around here for about $850,000.
I would like to add to that: The Technician: I will MAKE it work. I know lots of engineers who know how to design stuff, but not how to actualy build it or fix it. ---------------------------------------------------------------------------- I do agree that Conventional flow is easier to design for, and is the norm, but that is simply because that is what people started with. It would be just as easy to design for electron flow if conventional flow never existed. Think about it, a water pumping station (nothing to do with gravity) pumps water to your house, then from your house it goes to a lake, river or pond. It would be backwards to suck the water from a lake -through your house- and back to the plant. It seems backwards to think that when you turn on your computer, it is sucking electrons out of the earth, through your PC, and out to the power plant, but that is essentialy what is happening. The power plant is essentialy a huge electron hole maker, rather then electron generator. (taking A/C out of the picture)
*cough* speaking as an underpaid physicist... The water/gravity analogy is perfect. Just like we call voltage "potential", we do the same with gravity (remember 'potential energy'?) it's all the same. Zap's analogy is kinda off IMO. That goes back to the idea that it's the relative potiental difference that matters, not the absolute potential. The main difference is that there is no other way to characterize flow than saying the amount of volume or mass of fluid in a given direction. There's no negative counterpart to this. If we had some imaginary stuff with negative mass flowing in one direction, then we could say the actual mass flow is in the opposite direction, like with the flow of electrons vs. flow of charge. Ah, but remember we are getting AC out of powerplants and the wall, not DC!
You know he did say "taking A/C out of the picture I don't care either way, as long as my circuit works I'm happy. And conventional flow works for me. EDIT: Damn Zap you beat me to it
The Redneck: I already did that with beer cans and duct-tape...... About the gravity analogy: If you already have a good grasp of astrophysics, then yes, the gravity analogy is not that bad. The analogy of water in a tank (not reffering to Zaps water pump analogy) that is most commonly used does not work well. People can understand the simplest of flow this way, but get extremely confused when dealing with negative voltage. Zaps analogy using a water-pump is slightly better. Its a good representation of a voltage source with one exception: When dealing with voltage, you can add voltages in series where-as you cannot do so with gravity sources. At least, theres no easy way to explain it to those trying to grasp the ideaology of circuit theory.
but you can add series "voltages" with a pump (ex. multistage compressor) so for now, a pump analogy is pretty good. actually, i’m in the middle of writing a basic electronics-for-modders tutorial, using a water cooling setup as the example for current, voltage and resistance. LOL
From an Electrical Engineering perspective: design is done with "conventional" flow. The kicker is that currents can have negative values, meaning they're flowing in the direction opposite that you define to be the "refererce" direction. it's a pain in the ass to try and design for electron flow - just don't bother. In transistor physics, we talk about flow of "electrons" and "holes", holes being made-up positive particles that represent the lack of an electron. You can think of conventional current as "hole" flow if you want (be aware that a "hole" doesn't really exist in this way; holes are just a vacancy in the lattice of silicon atoms in semiconductors.) but it's easier to think of conventional flow because then it'll always go from the highest voltage to the lower voltages in a circuit. edit re: Zapho's post: the way EE classes are taught semiconductor physics is to abstract those "negative" particles and actually deal with them, all the while understanding that they don't physically exist. but we still generally speak of current flow in the "conventional" sense, that is, opposite what the electrons are doing. edit2: I'm sorry, but this makes my brain hurt. There's absolutely no difference: if you're really that into it, just swap the reference directions on the current flow and call it a negative current. for example with ohm's law, V=IR: if you have a LED hooked up across 12V with a resistor, "conventional" current is flowing down from 12 through the resistor and LED and to 0, so the voltage drop is (starting V - ending V), or 12 - 0 = 12. The current is whatever it comes out to using V=IR (you factor in what the LED voltage should be and so on.) But! Now think of it this way: swap the "direction" current is flowing, i.e. make it go from the 0V to 12V. The drop now is still (start - end): 0 - 12 = -12. Plug this into V=IR: R is still positive, so I becomes negative, right? Guess what: your negative "electron" current... is actually flowing the SAME WAY as the "conventional" current in the first place! here's a little picture cause I'm procrastinating: That's the way we were taught to think of it circuit theory. you just have to be consistent throughout - in the previous example getting -12 for the voltage drop in the "electron" direction, you see? the numbers and equations are all set up for "conventional" because that's how everyone calculates things. but re: quote, no, they'd just be the same, except all the numbers would be backwards. as demonstated above. When you really get into circuit analysis no one worries about what directions the electrons are ACTUALLY going, because it doesn't matter. (Until you start getting to transistor design and microelectronics, which is actually applied physics in disguse ) changing how we think of it isn't going to modify physics -- it might make circuit design more in tune with what's actually going on (and easier to learn if you're coming from a physics background), but it's not going to make the devices more efficient in any way. so I hope that clears things up a bit - basically, the point is, yes, electrons go the other way, but no one really cares that much because analysis works just the same this way. damn it now I have to go do my semiconductor physics final exam which is on exactly this topic
