It doesn't really matter which direction the electrons are moving, because the concepts of voltage drop, electric fields, magnetism, and all the physical world that they interact with behave as we expect them to. electron acceptor in photosystem II to photosystem. By the time science understood that electric current was the movement of negatively charged electrons, it was too late to change the standards, the textbooks, the schematic diagrams, and the generally accepted theory. All Rights Reserved. When I graduated from that training program, I went back to my old habit of conventional flow notation, primarily for the sake of minimizing confusion with component symbols, since vacuum tubes are all but obsolete except in special applications. Otherwise, the diode blocks all electron flow just like a break in the circuit, and the lamp will not glow. In most cases, this is little more than a historical curiosity. They even function well on alternating current (AC), where the direction changes rapidly over time. I then have them shift one chair (flow) in the direction of the empty chair. In on the perpendicular line, out the back of the arrow. If you had a fist approx. Too many vocational courses get hung up on electrons flowing and confuse the hell out of students. Calculate the wavelength of light used in a double-slit experiment with a slit separation of 5.6m and a spacing of 28cm between 3 light ? I will be a ghost forever. Later, when I began my first formal training in electronics, my instructor insisted on using electron flow notation in his lectures. His preference was not arbitrary, though. Still, I sometimes wonder if it would all be much easier if we went back to the source of the confusion -- Ben Franklin's errant conjecture -- and fixed the problem there, calling electrons "positive" and protons "negative.". Uh, no, I think you fail to understand. alternative path called cyclic electron flow, which uses photosystem I (P700) In fact, he asked that we take our textbooks (which were illustrated using conventional flow notation) and use our pens to change the directions of all the current arrows so as to point the "correct" way! but not photosystem II (P680). These devices work on the phenomenon of electrons hurtling through a vacuum, their rate of flow controlled by voltages applied between metal plates and grids placed within their path, and are best understood when visualized using electron flow notation. So generally speaking hole flow is the conventional standard, but so long as you understand both and know which convention is being used you're good. "Hole flow" is just silly. On a positive note (no pun intended), I have subsequently discovered that some students prefer electron flow notation when first learning about the behavior of semiconductive substances. I’ll get back to the basics, take a look at both, see how each works, and squash this debate once and for all. The term hole flow is usually only applied to semiconductor physics. Ano ang mga kasabihan sa sa aking kababata? As one might guess, polarized device symbols typically contain an arrow within them, somewhere, to designate a preferred or exclusive direction of current. ", My answer would be normally be against the arrow. That causes a positive charge on the atom, which will attract an electron from a neighbouring atom from the more negative side. How long will the footprints on the moon last? I've been working on electronics (mostly RF equipment) for 15 years, so I'm very good at theory. Ideally, a diode provides unimpeded flow for current in one direction (little or no resistance), but prevents flow in the other direction (infinite resistance). photosystem I (P700). The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. They set up an interference pattern in which a point on the 2nd nodal line is 29.5cm? The more I think about it, the more I need to look at some circuits. In a semiconductor however the line is heavily packed , a bit like you might see in a traffic jam, and the way holes work is with the arbitrary illusion that the one hole in the line is sort of like a particle going against the electron flow. All electrical engineering (EE) schools (in the US or elsewhere) have long used "conventional current" rather than "electron current", which are equivalent to "hole current". almost. When Join Yahoo Answers and get 100 points today. I have always seen it that current flows from high potential (voltage) to low in a circuit. What is the rising action of faith love and dr lazaro? Conversely, any device that functions differently on currents of different direction would be called a polarized device. Who is the longest reigning WWE Champion of all time? In the other direction (that is, n-type to p-type), the electrons do not see holes to enter the semiconductor material and the diode acts as an insulator. So you can imagine a flow of people following the path in order. Concepts of voltage, current, resistance, continuity, and even mathematical treatments such as Ohm's Law (chapter 2) and Kirchhoff's Laws (chapter 6) remain just as valid with either style of notation. while the flow of electrons are known as electrons flow. Most of them are made of so-called semiconductor substances, and as such aren't examined in detail until the third volume of this book series. primary electron acceptor of photosystem I passes the excited electrons to The chloroplast shifts to this process when the ATP supply drops and the The debate rages on. And perhaps by the end of this post still won’t add up. level of NADPH rises. Thank. Generally in my experience in the US we're concerned with current flow moreso than electron flow, so in most fields we use the conventional hole flow (+ to -). Holes flow one way, electrons the opposite. These holes are empty areas that the electrons can flow through in order to allow the material to act as a conductor rather than an insulator. Figure 1: Electron Flow and Conventional Current Flow It is important to realize that the difference between conventional current flow and electron flow in no way effects any real-world behavior or computational results. in the reaction center chlorophyll (P680) is captured by the primary Incandescent lamps (the type utilizing a thin metal filament that glows white-hot with sufficient current), for example, produce light with equal efficiency regardless of current direction. ATP, the Calvin cycle will slow or even stop. Because engineers from long ago have settled on conventional flow as their "culture's" standard notation, and because engineers are the same people who invent electrical devices and the symbols representing them, the arrows used in these devices' symbols all point in the direction of conventional flow, not electron flow. Orders Received by 1:00PM ET Weekdays, Ship Same Day, Customer Service Available Monday- Friday 9am - 4pm ET. Being that most analyses of electric circuits do not depend on a technically accurate depiction of charge flow, the choice between conventional flow notation and electron flow notation is arbitrary . As Some say conventional current flow is correct. You never wondered why current flowed into the source and out of the drain of an N MOSFET? In electron flow notation, we follow the actual motion of electrons in the circuit, but the + and - … Not wanting to confuse students by teaching "differently" from the other instructors, I had to overcome my habit and get used to visualizing electron flow instead of conventional. . Years later, when I became a teacher of electronics, the curriculum for the program I was going to teach had already been established around the notation of electron flow. This is how I intro the concept of hole flow: I have n students sit in a row of n+1 chairs. Many textbooks are available in both formats. Each An Why don't libraries smell like bookstores? Note: this does not say whether current flows from - to + or + to - (voltage). a glacier moves a the rate of 43.0 meters per year. It's like a line of people getting on a bus. © 2020 National Imports LLC, dba Magcraft. That is to say, all of these devices' symbols have arrow marks that point against the actual flow of electrons through them. In general, analyzing an electrical circuit yields results that are independent of the assumed direction of current flow. level is harnessed by the thylakoid membrane to produce ATP (by So as electrons flow one way, the holes "flow" in the opposite direction. photophosphorylation. Oddly enough, this was due in part to the legacy of my first electronics instructor (the 20-year Navy veteran), but that's another story entirely! However, because we tend to associate the word "positive" with "surplus" and "negative" with "deficiency," the standard label for electron charge does seem backward. the electrons that the chlorophyll molecule lost when it absorbed light This is where the competing notations of conventional and electron flow really matter. You can think about current as the flow of electrons, which go from negative to positive, or as the flow of holes, which go the other way. Not really, so long as we're consistent in the use of our symbols. Since I'm transitioning into a civilian career in electronics, I must know: Is the US standard electron flow (- to +) or hole flow (+ to -)? So in working on my foxhole radio - I realized I needed to look at diodes a bit more as I was making essentially a DIY diode with the pencil and razor blade. Oh well, sometimes you just can't win! Hole flow is the same thing as electric current, which is in the opposite direction of the actual flow of electrons. Since they have different densities, one floats on top of the other. Without sufficient TYVM. When Because I wanted my book to be a useful resource for my students, I begrudgingly changed plans and illustrated it with all the arrows pointing the "correct" way. an electron hole in the chlorophyll a molecule in the reaction center of chemiosmosis). That is, rather than discuss the direction the electrons are traveling (which would be the opposite direction of the electric current), we discuss the direction the holes are "traveling". enzyme extracts electrons from water and supplies them to P680, replacing Then the person behind the free tile steps on said free tile and the gap is now another tile behind. Let’s bust this thing wide open. This became known as conventional flow notation: Others chose to designate charge flow according to the actual motion of electrons in a circuit. I am an electrical engineer. This way the labels make sense, but the direction of charge flow is incorrect. Imagine people as electrons walking a line on that floora bit like a really long hopskotch game xD Now, in both situations the electrons move in the same direction, the difference is that in a normal conductor the line of people/electrons isn't too crowded, and it's easier to be traversed by said charged particles. Perhaps the best example of a polarized device is the diode. The students are modeling electrons in a metal/wire. Still have questions? When Benjamin Franklin made his conjecture regarding the direction of charge flow (from the smooth wax to the rough wool), he set a precedent for electrical notation that exists to this day, despite the fact that we know electrons are the constituent units of charge, and that they are displaced from the wool to the wax -- not from the wax to the wool -- when those two substances are rubbed together.
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