Electron Flow OR Conventional theory - Page 1
Forum section: electronics / general

author: kientructayho
author_rank: Newbie
timestamp: May 15, 2019, 04:50:56 am
content: Tiêu chuẩn cho một khách sạn mini cơ bản đó là phải có thang máy. Thế vậy thì trong khách sạn mini lắp thang máy kích thước thế nào, tải trọng bao nhiêu kg?Khách sạn mini cũng cần lắp đặt thang máy. Nên lắp đặt loại thang máy nào? Kích thước hố thang máy bao nhiêu là phù hợp? Toàn bộ thông tin được website Kiến trúc Tây Hồ tổng hợp trong bài viết này:https://kientructayho.vn/kich-thuoc-thang-may-khach-san-mini/nếu là người làm nghề kinh doanh thì có thể dễ dàng nhận thấy rằng trong những năm gần đây lượng khách lưu trú nội địa và quốc tế tăng trưởng vô cùng mạnh. Điều này thúc đẩy sự phát triển mạnh mẽ của hệ thống khách sạn, nhà hàng. Đặc biệt là khách sạn mini. Năm 2019, hàng loạt các công trình khách sạn mini được đầu tư xây dựng. Tập trung nhiều tại các khu vực như Hạ Long, Vân Đồn, Cát Bà, Sầm Sơn, Quy Nhơn, Phú Quốc…Có thêm một vấn đề khá quan trọng mà không thể thiếu trong thiết kế khách sạn mini đó là hệ thống thang máy. Thiết kế thang máy trong khách sạn là rất cần thiết để phục vụ việc di chuyển đi lại giữa các tầng thuận tiện và nhanh chóng hơn. Đồng thời thang máy cũng góp phần tạo điểm nhấn cho không gian nội thất của khách sạn.Đặc điểm của khách sạn mini là quy mô nhỏ. Chính vì thế khi lắp đặt nên cân nhắc lắp đặt thang máy có kích thước phù hợp. Thông thường, loại thang máy được sử dụng là loại thang cỡ nhỏ. Lý do bởi loại thang này tiết kiệm diện tích xây dựng hố thang máy, tiết kiệm điện năng.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 15, 2019, 05:28:09 am
content: It doesn't matter. The sign of the charge carrier is irrelevant in electromagnetism (i.e., Kirchhoff's laws).Also, while all metals have electrons as the charge carriers (sort of -- with no band gap there isn't clear separation between hole and electron states) , semiconductors can have both with the dominant carrier dependent on doping N or P type. Despite still being based on electron behavior behave for all practical purposes P type semiconductors act like they have positive charge carriers e.g., with the hall effect. For that matter, the 'electrons' in solid state physics (metals or semiconductors) i.e., occupied states of the band structure are not really electrons, but quasi particles representing collective behavior of electrons interacting with the lattice of positively charged nucleii -- as seen by their effective mass deviating from the bare electron mass.Basically you aren't wrong that at an atomic level only the electrons move, but any insight you think you get from thinking about electron current being "more right" than conventional current is wrong unless you are talking about vacuum tubes. Maxwell's equations don't care about what particles are moving, only net charges and currents. Metals in all practical electronic circuits are well described by simple resistivity, while describing semiconductors requires both positive and negative quasiparticles.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 15, 2019, 05:35:17 am
content: Quote from: kientructayho on May 15, 2019, 04:50:56 amIndeed, the same with vacuum tubes.It was much more common in "tube" days to learn Electron Flow, which to me, just "feels right" when looking at Electronic devices.That said, we also learned about Conventional Current Flow.There was so much good work done in the early days where that convention was used exclusively, that all the "Right Hand Rules" & the "arrow head" symbol for the direction of current flow, etc, were unlikely ever to be reversed, so everybody lived with the difference.The whole basis of the theory of Electrical Machines, (DC motors, generators, etc) was devised using Conventional Current Flow.EEs are very attached to CCF, & would have us believe that teaching someone EF, will "only confuse them".Considering it took people about 20 minutes back in the late 1950s to learn the difference, & why we use CCF much of the time, I frankly think that excuse doesn't fly, unless people have less intelligence these days.

author: boB
author_rank: Frequent Contributor
timestamp: May 15, 2019, 05:40:06 am
content: Quote from: vk6zgo on May 15, 2019, 05:35:17 amI seriously wonder that myself !

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2019, 09:04:44 am
content: Quote from: kientructayho on May 15, 2019, 04:50:56 amFor a good reason. It's the way some electronics symbols are drawn, like diodes, BJT's, and actual current source symbols. It is the defacto industry standard.Most text books also use conventional current flow, although some are offered in both versions.

author: daqq
author_rank: Super Contributor
timestamp: May 15, 2019, 09:27:29 am
content: QuoteTo the best of my knowledge, all schools everywhere teach this, because this is the physical definition of current, it is the industry standard etc.Yes, it is flawed, the people who first discovered the phenomena screwed up as they had no knowledge of the existence of electrons (probably flipped a coin), but we are stuck with it. A switchover would be incredibly expensive (though I wouldn't mind it).https://xkcd.com/567/

author: Brumby
author_rank: Unknown
timestamp: May 15, 2019, 09:48:30 am
content: Quote from: kientructayho on May 15, 2019, 04:50:56 amThere are a great many people here who know exactly what this is all about. PAINFULLY so.As has been mentioned above - and in several other threads around the forum - the assignment of positive and negative in the early days of discovery got it wrong and Conventional current flow became the mechanism for describing circuit operation.Even after the error was identified, conventional current flow stayed in popular usage because there was already a pervasive body of work using it as well as there being an industry based on that premise ... AND BECAUSE IT WORKS. The only time youmightneed to consider electron flow is in thermionic devices or semiconductor design.

author: Nerull
author_rank: Frequent Contributor
timestamp: May 15, 2019, 12:50:01 pm
content: If you think electrons are the only mobile charge carriers or that positive currents can never flow than you don't know as much about electricity as you think you do and perhaps should not be trying to change conventions.Current is carrier agnostic. Just because negative charges flow one direction doesn't mean we should redefine current.

author: TimFox
author_rank: Super Contributor
timestamp: May 15, 2019, 01:17:32 pm
content: Conventions are important things that we should all follow: Red light to stop, drive on the right (in US), etc. are all decisions made arbitrarily in the past.

author: EEVblog
author_rank: Unknown
timestamp: May 15, 2019, 01:30:49 pm
content: I'll take the normal one thanks.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 15, 2019, 03:14:36 pm
content: Quote from: EEVblog on May 15, 2019, 01:30:49 pmThat'd be the left one ( or the top one as they are repositioned in this answer), then!

author: raptor1956
author_rank: Frequent Contributor
timestamp: May 16, 2019, 03:09:14 am
content: When the engineering was being formalized they did not know about electrons and the analogies we still use make sense with a flow from positive to negative. The common comparison to voltage is pressure that one can visualize as a reservoir of a given height -- if the height is higher the pressure is higher (voltage higher). Water flows from higher (more positive) to lower (less positive). So, back in the day, before anyone knew what an electron was, thinking of it like water they would have had to make a surprising guess that most current would wind up flowing negative to positive. And, like most things expressed in a given framework, so long as you remain consistent within that framework it will all work out just fine.Brian

author: innkeeper
author_rank: Unknown
timestamp: May 16, 2019, 03:21:25 am
content: words of wisdom: never touch hole flow.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 16, 2019, 03:26:00 am
content: I think of current like a pnuematic system, sucking and blowing.If there's only two poles for DC one is always pushing electrons and the other always pulling. For tubes it's always electron flow (becuase the electrons themselves are literally flowing through the tube), but the B+ can also be thought of as the "suction". It can get wonky with semiconductors too. For example a PNP transistor has a negative collector where it "collects" electrons. In fact, alot of germanium transisor circuits (mostly PNP) used positive commons. But NPNs have a positive collector, so what is it "collecting"?It must mean the charge carriers or the "suction".

author: Brumby
author_rank: Unknown
timestamp: May 16, 2019, 03:36:58 am
content: Quote from: Cyberdragon on May 16, 2019, 03:26:00 amLet's not add semantics to the discussion. It's bad enough as it is.

author: bob91343
author_rank: Super Contributor
timestamp: May 16, 2019, 04:40:08 am
content: The whole thing was started by Benjamin Franklin I think, who decided currents went one way when in fact electrons were the carriers and went the other way. So electrons got assigned negative charges.The whole thing boils down to writing equations. So conventional current became the way engineers worked, while technicians, who wrote fewer equations, used electron flow. It's an indicator of how a person learned electronics; the ones who use conventional current tend to have attended formal college, engineering school if you will.With most tubes/valves, the flow is electrons but they are negative charges and so represent current flow in the other direction. With semicoonductors there is no specific direction because it depends on what devices are being used, and so the conventional approach makes more sense.There is a certain amount of prejudice here as well. You can guess where a person learned circuit theory by which way he draws the arrows.

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 04:40:48 am
content: There's a reason it's called "conventional" flow.

author: soldar
author_rank: Super Contributor
timestamp: May 16, 2019, 07:44:53 am
content: Quote from: Cyberdragon on May 16, 2019, 03:26:00 amDonations from the emitter. It's all for a good cause.

author: soldar
author_rank: Super Contributor
timestamp: May 16, 2019, 07:45:40 am
content: Quote from: james_s on May 16, 2019, 04:40:48 amBecause it's convenient?

author: daqq
author_rank: Super Contributor
timestamp: May 16, 2019, 08:28:25 am
content: QuoteIs this a common thing? I have never actually seen anyone draw arrows the 'electron' way here.

author: Brumby
author_rank: Unknown
timestamp: May 16, 2019, 11:01:07 am
content: Quote from: daqq on May 16, 2019, 08:28:25 amI hadn't noticed before - but now this statement is made, I can honestly say I do not recall anyone talking about electron flow in favour of conventional current flow outside of discussion such as this.

author: GlennSprigg
author_rank: Super Contributor
timestamp: May 16, 2019, 12:53:05 pm
content: GRRRRR...... !!!This "gets my goat" so much that I now have a 'Herd of Goats' bigger than the state of Texas,that must be worth a few Million Dollars by now, when I choose to sell them !!!!!!!!We ALL know that 'diagrams' for Valves, Transistors, Diodes etc STILL show 'Conventional' flow,but the question is WHY !!! Ok... they 'thought' that's how it worked, 'then'... however, NOWwe know different. I'm in my mid-60's now, but I remember when 18 or 19, that 'instructors'were trying to explain.... "Well, don't think of it as'electron' flow, but a 'reverse' movementof "Positive-Holes". Even 'I' then, knew this was total crap. Drawings need to change !!!!!!!!(Off my soap-box now... or maybe not)P.S. (Tongue in cheek here, but 'factual'), talking about 'Texas' in my 1st sentence........There are privately owned individual 'Cattle-Stations' here in Australia, that are each bigger thanthe whole State of Texas !

author: rstofer
author_rank: Super Contributor
timestamp: May 16, 2019, 03:15:23 pm
content: Quote from: kientructayho on May 15, 2019, 04:50:56 amIt isn't! It's been debated to death for generations.If we consider '+' to be 'higher' than '-' (an intuitive view) then current flowing from higher voltage to lower voltage makes sense in a physical way. Drop a ball, you don't expect it to go up. In some reference frames it could indeed move upward but from our daily lives we expect it to go down.It truly doesn't matter but I imagine CCF dominates discussions.

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 03:49:00 pm
content: I've known since I was probably 12 years old that electrons flow from negative to positive but that in most cases we pretend it's the other way around and schematics are drawn that way. Never seemed difficult to grasp and certainly not as confusing as trying to change it now. Unless you're working with vacuum tubes or designing semiconductors you don't even need to know.

author: soldar
author_rank: Super Contributor
timestamp: May 16, 2019, 08:05:57 pm
content: Only if you are working at the atom physics level you need to take into account these things. Otherwise it makes no difference. If you are inventing or perfecting vacuum tubes, transistors or whatever then yes, you better know exactly the fundamentals of how and why they work but as a designer of circuits that use components it makes no difference. In my world current flows from anode to cathode. So sue me!

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 16, 2019, 08:49:53 pm
content: Quote from: soldar on May 16, 2019, 08:05:57 pmAh, so the NPN collector collects the little pixies that carry the electrons then.

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 09:56:50 pm
content: It doesn't matter what the NPN collector emits, for all practical purposes you can assume it collects current.

author: schmitt trigger
author_rank: Super Contributor
timestamp: May 16, 2019, 10:07:24 pm
content: I use EF when I am looking at vacuum tube circuits. They make so much more sense that way.For everything else, which is 99-plus% of the circuits, I use CCF.

author: Brumby
author_rank: Unknown
timestamp: May 17, 2019, 12:48:21 am
content: Quote from: GlennSprigg on May 16, 2019, 12:53:05 pmI understand your angst, but the answer is something I (and others) have already stated:Quote from: Brumby on May 15, 2019, 09:48:30 amWhich means there is too much material already in existence to contemplate changing it all and there is no PRACTICAL reason to even consider it. It is merely an academic irritation.

author: EEVblog
author_rank: Unknown
timestamp: May 17, 2019, 02:18:20 am
content: Quote from: raptor1956 on May 16, 2019, 03:09:14 amAnd now that we know we basically don't care, because for most purposes the defacto standard conventioncurrent flowworks just fine.Note it's calledcurrent flow, notelectronflow.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 17, 2019, 03:20:44 am
content: But what if you have a dual polarity amp supply? Wouldn't you have both in the same circuit since the common is neutral and both poles flow towards it?

author: james_s
author_rank: Super Contributor
timestamp: May 17, 2019, 03:54:18 am
content: Quote from: Cyberdragon on May 17, 2019, 03:20:44 amWhat makes you think that? You don't have neutral, you have a positive supply, a negative supply and ground. Conventional flow says that current flows from positive to negative, so in this case it flows from positive to ground and from ground to negative, the rules don't change.

author: Brumby
author_rank: Unknown
timestamp: May 17, 2019, 04:01:53 am
content: Indeed. You would have the same "problem" whether you talk in terms of conventional current flow or electron flow. The only difference would be the sign of everything. The mathematical description and Kirchhoff's laws still apply without difficulty.

author: EEVblog
author_rank: Unknown
timestamp: May 17, 2019, 04:05:06 am
content: Quote from: Cyberdragon on May 17, 2019, 03:20:44 am"Ground" or "common" is just an arbitrary reference. The voltage on "common" with respect to the negative terminal is more positive, so current flows from the more positive "common" to the negative.This issues still remains regardless of conventional or electron flow.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 18, 2019, 03:47:07 am
content: Not really a useful contribution, but it is delightfully apposite.I was just over on Whirlpool, where there is a thread on the Australian Federal Election.One poster:-"...... that's when I thought the electron was a foregone conclusion......"Don't you just love spellcheck/ word suggestion?

author: innkeeper
author_rank: Unknown
timestamp: May 18, 2019, 03:27:22 pm
content: There is an alternate universe were electrons are called positrons and positrons are called electrons and conventional flow and positron flow are the same things.let's start the positron movement...You may say I'm a dreamer, but I'm not the only one. I hope someday you'll join us. And the world will live as one.

author: retrolefty
author_rank: Super Contributor
timestamp: May 18, 2019, 04:06:29 pm
content: Quote from: EEVblog on May 17, 2019, 02:18:20 amLOL, so what is specifically flowing in this 'current of flow'? Oh Iknow it's electrons swimming backwards.

author: bob91343
author_rank: Super Contributor
timestamp: May 18, 2019, 05:49:41 pm
content: The conventional method works when you are writing equations. Nobody really thinks there is a flow that way, although certainly situations exist like that. The conventional method takes care of it without having to decide what is flowing, ions, electrons, holes.I can drive a car that has a carburetor but frankly I never fully understood how those things work. I had a discussion about this with a couple of non-electronic engineers. They said they had trouble visualizing these electrons so that they could understand circuitry. I replied that I had that problem with carburetors. So we stared at each other wondering whether it was harder to visualize gaseous motion or atomic particle motion. We each said we had no trouble with what we were comfortable with but couldn't get it with the other stuff. We each said 'but you can't see it!' and realized we were saying the same thing.The mind works in strange ways.

author: dmills
author_rank: Super Contributor
timestamp: May 18, 2019, 06:59:40 pm
content: Thing is electrons are the charge carrier in metals, but in a lot of electrochemistry (Which up until fairly recently was the elephant in the room for energy consumption), the charge carriers are ions which DO follow conventional current flow!Between the Chloralkali process and aluminium smelting electrochem is a HUGE industry.Seriously, the only people who care are chemists and some semiconductor and particle physics types, everyone else can just ignore the issue and know that the math works either way.Besides if you figure out how fast electrons drift along in a copper conductor at any current you would want to run, it is so slow that it hardly counts. Seriously, calculate what the mean drift velocity is in say a 1mm^2 wire @ 1A, it is WAY lower then you would probably expect, this calculation is eye opening.Regards, Dan.

author: james_s
author_rank: Super Contributor
timestamp: May 18, 2019, 07:03:57 pm
content: Quote from: retrolefty on May 18, 2019, 04:06:29 pmIt doesn't matter, it's an imaginary construct to aid visualizing how a circuit works. Current flows, it's irrelevant what current actually is, or if it exists at all. The world is full of imaginary concepts used to measure, describe and understand various things.

author: bob91343
author_rank: Super Contributor
timestamp: May 18, 2019, 07:15:07 pm
content: Electrons flow slowly in aggregate but it's kind of like water. Being incompressible, the propagation velocity is high. So when you open the cold valve in the tub, the water nearly immediately changes flow rate, but the temperature coesn't change right away.The current in a wire is the same; it changes almost immediately in quantity but a given electron doesn't move that fast.

author: dmills
author_rank: Super Contributor
timestamp: May 18, 2019, 08:59:34 pm
content: In a metallic conductor that electron probably drifts more slowly then the water coming out of your tap (True, do the sums)!Really, we mostly concern ourselves with the fields and waves between conductors, not tiny little statistical bits of charge bouncing around inside them.Water is compressible (Otherwise longitudinal waves, like say sound) would not propagate, granted it is not very easy to compress but that just makes for a high longitudinal wave propagation velocity.Regards, Dan.