Direction of Current? - Page 1
Forum section: electronics / beginners

author: JeffL1
author_rank: Newbie
timestamp: September 21, 2024, 05:21:32 am
content: I can't get my head around this? Current travels from Positive to Negative, but electrons travel from Negative to Positive. I thought current was the flow of electrons. What does this all mean?

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2024, 05:27:42 am
content: use a compass and right hand rule to find direction of current flow (ignore schematic)

author: langwadt
author_rank: Super Contributor
timestamp: September 21, 2024, 05:33:44 am
content: they guy that first defined the direction of current flow screwed up and we are stuck with, but it doesn't really matter it is just the way it is

author: David Hess
author_rank: Super Contributor
timestamp: September 21, 2024, 07:39:39 am
content: Quote from: langwadt on September 21, 2024, 05:33:44 amWasn't the guy Benjamin Franklin?

author: PGPG
author_rank: Frequent Contributor
timestamp: September 21, 2024, 08:08:45 am
content: Quote from: JeffL1 on September 21, 2024, 05:21:32 amPeople defined current flow direction when they didn't know that really traveling objects (electrons) are negative.

author: tszaboo
author_rank: Super Contributor
timestamp: September 21, 2024, 08:15:21 am
content: It is called technical current or conventional current. For most electronics, the electron current is irrelevant, since it's only relevant for cathode ray tubes or talking about how a transistor works. So just forget about the electron current.

author: wasedadoc
author_rank: Super Contributor
timestamp: September 21, 2024, 08:28:51 am
content: At the macroscopic level, negative charges moving in one direction look pretty much thr same as positive charges moving in the opposite direction.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2024, 08:36:29 am
content: there might be a hole in your theory

author: djsb
author_rank: Super Contributor
timestamp: September 21, 2024, 10:02:34 am
content: Search for Richard Feynman electricity.

author: Xena E
author_rank: Frequent Contributor
timestamp: September 21, 2024, 12:51:19 pm
content: Current doesn't travel, or flow, anywhere: it's just a quantification of energy flow at a point in a circuit.

author: TimFox
author_rank: Super Contributor
timestamp: September 21, 2024, 01:55:17 pm
content: Electromagnetism was developed in the mid-19th century, culminating in work of Maxwell and Heaviside (q.v.), starting from previous work by Faraday and others.Current is a scalar, with a positive or negative sign.It is defined in physics as an integral over an area of the scalar product of the current density vector and the area vector normal to the area.This was before the electron was discovered in 1897, and shown to have a negative charge using the existing definition of voltage and current polarity.As can be found in elementary textbooks, the flow of electrons is one form of current, but the flow of positive ions is also an electrical current.The easiest forms to consider are electrons through a vacuum tube, or ions in a particle accelerator vacuum: current through solids (copper and semiconductors) is a more complicated process (solid-state physics).I think of current in a wire as a slight tendency of a gazillion electrons to move to the right, making a current flowing to the left, as a result of a voltage gradient along the wire.

author: Marco
author_rank: Super Contributor
timestamp: September 21, 2024, 02:23:08 pm
content: Quote from: TimFox on September 21, 2024, 01:55:17 pmThat turns it on its head. Currents through solids can sometimes be simplified by not thinking in terms of moving electrons.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 21, 2024, 04:12:50 pm
content: It is all an agreement between people discussing the subject, and sometimes one way works better than the other. There is nothing absolutely fundamental about either definition so don't get to worked up about it. The only really important thing is to stay consistent within any single analysis. And then be careful when copying or transferring results from one analysis to another.

author: TimFox
author_rank: Super Contributor
timestamp: September 21, 2024, 04:13:30 pm
content: Current and charge are concepts that are more general than are individual types of charge carriers (e.g., electrons and ions).The motion of electrons in a cathode-ray vacuum tube is a very easy type of current to understand: solid-state physics is more complex.Changing the definition of the polarity of charge to make electrons positive would require re-labeling every voltmeter in the world, to no good purpose.

author: SteveThackery
author_rank: Super Contributor
timestamp: September 21, 2024, 04:28:39 pm
content: The "direction" of current was defined as flowing from positive to negative at a time before electrons were discovered. When they were discovered, it was found that they flow from negative to positive. Rather than redefine the "direction" of current - which would have had numerous knock-on effects - they just shrugged their shoulders and said "Oh, well, let's call it "conventional" current that flows from positive to negative."It almost never matters unless you are designing a new semiconductor, or a device to perform electrolysis, which way the electrons flow. You can safely use conventional current in your electronic circuit designs and calculations.

author: Marco
author_rank: Super Contributor
timestamp: September 21, 2024, 04:37:30 pm
content: Quote from: TimFox on September 21, 2024, 04:13:30 pmHoles are abstraction, not generalization.You can fire an electron through a vacuum, you can't a hole ... it generally doesn't exist.

author: Zero999
author_rank: Super Contributor
timestamp: September 21, 2024, 04:41:00 pm
content: Quote from: SteveThackery on September 21, 2024, 04:28:39 pmThought experiment: would electronics be any different today, if the direction was correctly in the first place? Would we be using negative voltages for single supply circuits?

author: m k
author_rank: Super Contributor
timestamp: September 21, 2024, 05:32:52 pm
content: Energy flows, it has power and it can do work.When energy hits antenna it create disturbances, it force electrons to move away from their comfort zone.That creates a chain effect and what?Electron that was in old place is now in new place, generally.If old place is without a new electron there is a positive imbalance, generally.New place then has a negative imbalance, generally.It's much easier to talk without a constant minus sign.

author: IanB
author_rank: Super Contributor
timestamp: September 21, 2024, 05:39:59 pm
content: Seems like this was a drive-by thread-bombing, and everyone took the bait?

author: m k
author_rank: Super Contributor
timestamp: September 21, 2024, 05:48:28 pm
content: Used energy is still pretty low.

author: Neilm
author_rank: Super Contributor
timestamp: September 21, 2024, 06:28:42 pm
content: Obligatory XKCDhttps://xkcd.com/567/

author: JeffL1
author_rank: Newbie
timestamp: September 21, 2024, 06:30:18 pm
content: "drive-by thread-bombing" is a new term for me. I wasn't doing that. Thinking in terms of water current, I can't understand how water can move in one direction, but the current flows in the opposite direction. Just doesn't make sense.

author: PGPG
author_rank: Frequent Contributor
timestamp: September 21, 2024, 06:59:57 pm
content: Quote from: Zero999 on September 21, 2024, 04:41:00 pm

author: thephil
author_rank: Regular Contributor
timestamp: September 21, 2024, 07:02:45 pm
content: As others pointed out, current was defined well before we knew about electrons so things seem to be backwards.But that's OK – electrons are not the only way to carry charge around. they just happen to be the thing that flows through the wires we like to use. Current is just "something carrying charge is moving in some direction." – Ifsomethingis positively charged things are aligned. Ifsomethingis negatively charged, like electrons, things seem to be backwards. Just think of technical current as "positive charge moving in that direction" and then, obviously, negative things moving in the opposite direction amount to the same thing.

author: artag
author_rank: Super Contributor
timestamp: September 21, 2024, 07:08:20 pm
content: It's not so much that current was defined as wrong, but positive and negative. The direction and charge of a current-carrying electron are consistent, but if + and - had been give as names to the opposite battery terminals it would all have made sense, with electrons positively-charged and carrying current from + to -

author: wraper
author_rank: Unknown
timestamp: September 21, 2024, 07:09:34 pm
content: Electrons are not the only carrier of current, nor electrons have the same propagation speed (they're really slow, ~1mm/s in conductors). So argument that current direction must follow direction of electron flow does not have basis for it.

author: IanB
author_rank: Super Contributor
timestamp: September 21, 2024, 08:08:15 pm
content: Quote from: JeffL1 on September 21, 2024, 06:30:18 pmIf you touch an ice cube, does cold flow into your fingers, or does heat flow out of them? Does it make any difference?

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2024, 08:27:35 pm
content: I still say for practical purposes examine the magnetic field because that is the relevant part to engineering design.I think people find the theory of electron motion interesting and it might have uses to know this but not for general design of circuits, it is one of those things that annoys people to death that want to know about EE and don't do EE. The topic that comes up when you try to explain something to someone thats not practicing engineer or hobbyist for some reason, that you don't care about, no one you know cares about, but its a pressing issue for a theoretical math major.It just won't come up practically, but it will turn into a knife fight among theorists. I never get involved or try to stop it because maybe it will give us some new device to play with eventually if its explored (in the form of a strange effect, like GMR, Hall, Seebeck, etc), that can be used to make some electrical transducer/oscillator/generator/etc with that is a option to use in a circuit.. more then likely someone is going to try to turn it into boring "RAM" of some kind.

author: Xena E
author_rank: Frequent Contributor
timestamp: September 21, 2024, 09:08:27 pm
content: Quote from: IanB on September 21, 2024, 08:08:15 pmNo practical difference at all, and it's just best to use whatever mental model is simplest for the problem at hand.Being asked the question by a lay person who has no real interest in physics, it is always a case of how quickly their eyes glaze over when you start talking about the laws of thermodymanics.

author: tggzzz
author_rank: Super Contributor
timestamp: September 21, 2024, 09:38:21 pm
content: Quote from: JeffL1 on September 21, 2024, 06:30:18 pmStandard school physics question... There is a 13A current flowing; how fast are the electrons moving.Later on you realise the energy isn't carried by electric current in wires, but by the electromagnetic fields surrounding the wires. If the wires don't exist, the EM fields still carry the energy but it isn't guided.

author: golden_labels
author_rank: Super Contributor
timestamp: September 21, 2024, 10:27:31 pm
content: Quote from: IanB on September 21, 2024, 05:39:59 pmComplete with the obligatory posts of people, who argue what “is real” while missing the 2300 years of development in epistemology and metaphysics?

author: Benta
author_rank: Super Contributor
timestamp: September 21, 2024, 10:38:08 pm
content: Quote from: IanB on September 21, 2024, 05:39:59 pmBest answer yet. Interesting to see how people dive down a rabbit hole from a troll or AI something.I'm waiting for the next "How do Magnets Work" bait-posting.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2024, 11:24:29 pm
content: its a really common thing for people to be confused and interested by magnets I see it in real life all the time

author: JeffL1
author_rank: Newbie
timestamp: September 21, 2024, 11:45:17 pm
content: Quote from: Benta on September 21, 2024, 10:38:08 pmI am neither a troll nor an "AI something". I was watching a presentation last night that showed current flows from positive to negative. It was the opposite of what I remembered being taught in high school (almost 60) years ago when we were taught that whoever named positive and negative got it backwards. I checked it on Google where I found that current and electrons move in opposite directions.As for the ice cube touching question, " Heat energy always flows from the warmer object to the cooler object.".

author: Benta
author_rank: Super Contributor
timestamp: September 22, 2024, 12:03:15 am
content: Quote from: JeffL1 on September 21, 2024, 11:45:17 pmIn that case, my apologies.But as a first poster with zero "street-cred" and a question that's been beaten to death over the last century, I hope you understand the reaction.In any case, Welcome to the Forum.

author: IanB
author_rank: Super Contributor
timestamp: September 22, 2024, 12:08:59 am
content: Quote from: JeffL1 on September 21, 2024, 11:45:17 pmIf electrons happen to move in the opposite direction to electric current, this is all relative. If you are sitting still in a train, and look out the window, you may see the scenery moving past the window. So are you moving forwards, or is the world outside the window moving backwards? How could you tell the difference?QuoteMaybe, but now, what is energy? And why can't we say that cold energy flows from the cooler object to the warmer object?

author: wasedadoc
author_rank: Super Contributor
timestamp: September 22, 2024, 12:17:29 am
content: Positive and negative whether applied to voltages, charges, numbers or anything else are only conventions. There is no absolute truth that electrons carry a negative charge. Just an agreement that it is the one of the two possible words ("positive" or "negative") everyone will use. The world would function equally well if the words "positive and "negative" were swappedeverywhere.

author: golden_labels
author_rank: Super Contributor
timestamp: September 22, 2024, 08:12:15 am
content: Quote from: JeffL1 on September 21, 2024, 11:45:17 pmIf that’s the case and it’s a honest question, please forgive my comment too. Unfortunately the internet is a place filled with people, who seek disruption, and this thread was uncanilly close to what they produce.(1)Let’s hope for better experience in the future.Quote from: JeffL1 on September 21, 2024, 11:45:17 pmWe may model the world in many ways. They are not always in line with each other. What you encountered is just two different models of the same thing. They are both right, and neither of them is “true reality” — they are mathematical abstractions.One treats current akin to a “mass noun”, like water in a river. Without concerning itself with details of what mechanism stands behind this large-scale, observed phenomenon. Just like you don’t consider each water molecule in a river. This model assumes current goes from positive to negative. The historical reasons for that were outlined by others. But be aware that whichever convention we choose, both are equally good. In fact such an arbitrary decision has to be taken while solving many circuits, and the results just come out as negative numbers.The other treats current as a flow of actual charges. In this model it’s important, what’s the average(!) direction to which specific charge carriers move. For example electrons and negative ions move from negative to positive. Holes and positive ions move from positive to negative. Inside a battery temporary products of the reaction may move either, depending on chemistry. In a changing magnetic field or in thermoelectric effect electrons are observed to move from negative to positive, but realize this polarity isn’t the driving force for their movement, but rather the consequence. It all matters, if you wish to gain deeper understanding of how particular devices operate. But is not needed to put their electronic behavior into use. Again, in this case opposite directions could be used with no harm to the model, but it would be pretty cumbersome to use. For the same reason why driving a car at -50 km/h or (35 - 35i) km/h, despite being mathematically valid, is not a widely used notion.(1)A seemingly beginner question, so easy to answer it brings not only a large number responders, but also those who themselves are beginners, from a new user with no reputation, and with no further inquiries/comments from that user.

author: Xena E
author_rank: Frequent Contributor
timestamp: September 22, 2024, 09:25:27 am
content: Quote from: Benta on September 21, 2024, 10:38:08 pmI hope you've got the Richard Feynman "you wouldn't understand if I told you" video link on standby.

author: Zero999
author_rank: Super Contributor
timestamp: September 22, 2024, 11:00:34 am
content: Quote from: JeffL1 on September 21, 2024, 11:45:17 pmYes, that's true. Electricity was discovered, along with the concept of charge, before the electron. They knew that electricity flowed between oppositely charged objects, long before the electron was known. They had to distinguish between oppositely charged objects, and used the terms positive and negative, but unbeknown at the time, it meant that electrons flowed from negative to positive, yet the opposite was assumed.To answer the question. All text books were written based on the assumption of current flowing from positive to negative. Then the electron was discovered and the reverse was proven to be true, but the convention stuck. No one wanted to re-write all of the old text books and new ones referred to the old ones, so it didn't make any sense to change. For most practical purposes it didn't make any difference whether the sign is positive or negative, or which way electrons flowed so the convention stuck, hence the term conventional current flow.Another thing to note is that in conductors, electrons aren't the only charge carriers. There are also holes, i.e. positively charged regions where electrons are missing. Holes flow in the opposite direction to electrons, so when one is talking about conventional current flow, they're referring to hole flow.https://en.wikipedia.org/wiki/Electron_hole?useskin=vector

author: wraper
author_rank: Unknown
timestamp: September 22, 2024, 12:09:02 pm
content: Quote from: Zero999 on September 22, 2024, 11:00:34 amReverse is not true, electrons are just a special case.QuoteHoles are not real charge carriers, it's just a concept. There are real positively charged particles that can carry the current. Such as ions, protons.

author: ejeffrey
author_rank: Super Contributor
timestamp: September 22, 2024, 04:18:07 pm
content: Quote from: JeffL1 on September 21, 2024, 05:21:32 amBasically ignore electrons. They are irrelevant for 99% of electronics, despite the name. The idea that conventional current is somehow "wrong" because electrons are negative is just a stupid meme and causes far more confusion than it "solves". It's a sign convention, and the choice of sign convention literally does not matter as long as it is used consistently including consistency with the related conventions for electric and magnetic field directions.Charge is a quantity that can be positive or negative, and gets pushed by electric and magnetic fields that are vector quantities, meaning they have a direction as well as magnitude. In normal electronics you only care about the net charge. Wires are full of positive and negative charges that almost but not perfectly cancel out. It's small imbalance we care about.When you have free charges such as in a CRT, vacuum tube, or electrochemical cells you may care about the absolute charge of individual carriers. For instance there is no such thing as an "anode ray tube" at least outside of CERN. But it still doesn't matter what sign convention you use.

author: TimFox
author_rank: Super Contributor
timestamp: September 22, 2024, 05:15:04 pm
content: "Charge" is a general concept, and "charge carriers" (e.g., electrons) are specific examples of objects that have a net charge.Both electrostatic force and gravitational force depend on 1/r122, the famous inverse-square law.However, gravitational mass is positive-definite (no such thing as gravitational repulsion), while electrostatic charge has two polarities.Before Franklin, in 1733 Charles Francois de Cisternay du Fay showed that charge had two types: "vitreous" (the result of rubbing glass with fur) and "resinous" (substituting amber for glass), and that like charges repelled each other and unlike charges attracted each other. Later, vitreous was defined as positive and resinous as negative, to go into Coulomb's Law for force.In those pre-atomic days, the two types of charge were treated as fluids.Newton (gravitation):F12=Gm1m2/r122and Coulomb (electrostatic)F12=Kq1q2/r122In Newton's law, the numerator is the product of two positive values and therefore positive definite.In Coulomb's Law, the numerator can be positive (++ or --) for repulsive, or negative (+- or -+) for attractive.(The formal vector equations for the two laws give the correct direction for the resulting forces.)Of course, any lump of normal matter you encounter is neutral (or damned close) in charge, with equal positive and negative charges.The charged balls used in Coulomb's torsion balance (capable of measuring small forces) had net charges far less than the individual totals of electrons (negative) and protons (positive) contained in the balls.Since matter consists of huge equal amounts of protons and electrons, it is a matter of convention as to which is positive or negative.Most elementary textbooks have an illustration of a current loop where different types of current are connected in series: for example, a vacuum diode, a copper wire, an ionic liquid solution, and the charge belt in a Van de Graaff accelerator.The important charge carriers differ in each branch of the circuit, but the current flows in the same path around the loop.

author: bson
author_rank: Unknown
timestamp: September 22, 2024, 11:44:24 pm
content: Quote from: JeffL1 on September 21, 2024, 05:21:32 amElectric current is flow of positive charge. Electrons are negatively charged, so for a positive charge to flow the electrons have to move in the opposite direction.It's also not just electrons, but anything with an electric charge, including proton plasma or positively charged holes, can form an electric current.

author: IanB
author_rank: Super Contributor
timestamp: September 23, 2024, 02:06:38 am
content: Quote from: JeffL1 on September 21, 2024, 05:21:32 amPerhaps you may have gathered by now from all the other answers, but electric current was observed and the laws of electricity were formulated before anyone had an idea that electrons existed. So if nobody had any idea that electrons existed, there was no way they could define current as the flow of electrons. So your premise is wrong.