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Using Arduino => General Electronics => Topic started by: MrMageeyee on Jun 07, 2018, 03:44 am

Title: Which direction does current flow?
Post by: MrMageeyee on Jun 07, 2018, 03:44 am
I am trying to map out a circuit, and I don't know if electrons** flow from ground to 5V or vice versa?  Thanks!
Title: Re: Which direction does current flow?
Post by: terryking228 on Jun 07, 2018, 03:50 am
Hi,

That is actually a good question and discussed a lot. In the 1880's especially.  

What is actually flowing is ELECTRONS, which are little negative charged particles. They are attracted by positive voltages. So ELECTRONS flow from "Ground" to "VCC" on an Arduino. This is "Electron Flow"..

BUT the OldSkool "Conventional Current Flow" assumes current (whatever THAT is) flows from Plus to Minus.

WikiPedia "Electric Current" 
(https://upload.wikimedia.org/wikipedia/commons/thumb/2/2e/Current_notation.svg/345px-Current_notation.svg.png)

The ELECTRONS really don't care, but get a charge out of all the arguments...
Title: Re: Which direction does current flow?
Post by: MrMageeyee on Jun 07, 2018, 03:51 am
Thank you! That was exactly what I was asking!
Title: Re: Which direction does current flow?
Post by: tinman13kup on Jun 07, 2018, 04:06 am
Oh NO! Hole flow, electron flow, it's maddening I tell ya!

I was taught electron flow, so current is from ground to positive potential.
Title: Re: Which direction does current flow?
Post by: DrAzzy on Jun 07, 2018, 04:23 am
It's worth noting that you really don't need to care which direction electrons are actually flowing (and engineers, in practice, rarely talk about that, just about positive and negative voltages and currents.

By convention, current flow is from positive to negative (convention set before we knew what electrons were)
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 07, 2018, 04:51 am
I agree with DrAzzy. As long as you assign polarity symbols for components (where necessary).... which means voltage polarity symbols, and current direction (arrow) symbols, and write down values of voltages (eg. +5V or -5V) and currents (eg. 2A or -2A), then we can just focus on analysing the circuit.... such as figuring out whatever we need to figure out.... like other voltages and currents or power within the circuit.
Title: Re: Which direction does current flow?
Post by: ted on Jun 07, 2018, 06:17 am
How about AC ? - LOL
Title: Re: Which direction does current flow?
Post by: DVDdoug on Jun 07, 2018, 06:29 am
First, I took electronics in high school and I learned that electrons flow from negative to positive.

Then I took electronics in college and learned that current flows from positive to negative.

Then I took college physics and I learned that current (electrons) flows from negative to positive.

...Finally, I understood that "conventional current" is a concept, and I understood that in the engineering world you've got to go-along with the convention.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 07, 2018, 08:11 am
How about AC ? - LOL
For AC circuits, the same deal applies. Still got to use a circuit sign convention..... eg. passive sign convention, for basic circuit analysis and design.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 07, 2018, 08:17 am
...Finally, I understood that "conventional current" is a concept, and I understood that in the engineering world you've got to go-along with the convention.
Having a general agreement (everyone following some sign/compatible convention) allows for consistency in results I guess.

For physics, I'm guessing that they could easily have said that electrons have 'positive' change. Definitions is what it is.

Somebody needed to say --- we got to make a choice..... let's go with this/it.

It's sort of name for right-hand left-hand..... we could easily have chosen the reverse of it.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 07, 2018, 08:50 am
Not sure if this was said -- didn't read all of the comments, so:

As others have said, there is the Electron Flow convention, AND the Conventional Current convention.  The bottom line, and important detail is: pick a convention and stick with it throughout the circuit.

I usually choose Conventional Current, because, then all the arrows make sense [on diodes, transistors, SCRs, etc.] ;)

In electronics, it usually doesn't matter which direction the current is flowing.  In physics you will probably care about that, but when designing circuits, just pick a convention and stick with it.
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 07, 2018, 09:00 am
Electrons don't really flow. They just jump to the next atom, which displaces another electron, etc., etc. The holes flow, but then holes aren't really anything.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 07, 2018, 10:23 am
Chris is right about that. Eg.... a parallel plate capacitor. During the charging and discharging stages, the electrons don't move across the 'gap' from one side of the plate to the other when a voltage source is applied across the two plates.
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 07, 2018, 11:14 am
And for added fun, while the current moves at light speed, the electrons (and holes) move in the tune of millimeters or centimeters an hour... if it's DC... in case of AC they're just moving back and forth, not going anywhere really!
Title: Re: Which direction does current flow?
Post by: MarkT on Jun 07, 2018, 12:19 pm
Electrons don't really flow. They just jump to the next atom, which displaces another electron, etc., etc. The holes flow, but then holes aren't really anything.
Depends what they flow in.

For a vacuum, electrons are in free fall but strongly dominated by any electric field (much much stronger
than gravity),
for metals and conduction band in semiconductors electrons flow - they are not bound to atoms.
Holes in semiconductors are more complex, since they emerge from bound (valence) electrons hopping
from atom to atom.  Holes are less mobile than electrons, and this I think is the principal cause (but
I may be wrong, solid state physics is not trivial!)

Unbound electrons in metals are actually moving around at random at _very_ high speeds(*) all the time, the
actual macroscopic current is a slow drift superimposed upon that.  Due to the electric field all the rapid
random electron motion is correlated and cancels out on the large scale, so we almost never have to worry
about this (fortunately).  These electrons occasionally scatter off some of the atoms (which is the cause of electrical resistance)

(*) copper has a Fermi velocity of around 1600 km/s, typical drift velocities in copper wires are measured
in mm/s, 9 orders of magnitude smaller.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 07, 2018, 03:09 pm
Electrons don't really flow. They just jump to the next atom, which displaces another electron, etc., etc. The holes flow, but then holes aren't really anything.
I think you're confusing current flow in a conductor with current flow in a semiconductor.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 07, 2018, 03:38 pm
And, to more properly answer the actual OP question: Actual physical direction of current flow depends on the "charge carrier" involved:
Title: Re: Which direction does current flow?
Post by: pwillard on Jun 07, 2018, 04:54 pm
We can blame Benjamin Franklin all day long for getting it wrong... but in the end... its just easier to use the "conventional" flow concept (Hole Flow, if you must) as it matches the direction that a DIODE in a schematic diagram will point.

Don't make me use diodes backward...   ;-P

Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 07, 2018, 05:26 pm
Quote
Ions [/i]are considered charge carriers, but even their charge is the result of a summation of the charges on protons and electrons [and, in fact, my smoke detector example is really an example of ions as charge carriers].
Another example of ions as charge carriers is in electrolyses, and in general the conductance of water.

Don't make me use diodes backward...   ;-P
Not just diodes... transistors as well.
Title: Re: Which direction does current flow?
Post by: ted on Jun 07, 2018, 06:15 pm
This
(https://eos.org/wp-content/uploads/2017/05/tower-lightning-human-made-towers.jpg)
and this
(https://whyfiles.org/wp-content/uploads/2013/10/wg_shstock_lightning_types.jpg)
Title: Re: Which direction does current flow?
Post by: pwillard on Jun 07, 2018, 07:59 pm
So the Answer based on TED's empirical evidence...

"Which way does current flow?"    -->  Whichever way it *can*.
Title: Re: Which direction does current flow?
Post by: ted on Jun 07, 2018, 09:17 pm
Bingo
Title: Re: Which direction does current flow?
Post by: MarkT on Jun 07, 2018, 10:06 pm
Holes, as mentioned above, are conceptual charge carriers.  They don't exist as a physical entity

You'd need to define "physical entity" fairly carefully to make that claim watertight, and probably
lose the baby with the bathwater in the process.  To a semiconductor physicist holes are very real...
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 07, 2018, 10:21 pm
Quote
To a semiconductor physicist holes are very real...
The are, they even have mass, which means the electrons in certain circumstances, have negitave mass. That means they are repelled by a gravitational field.

So go and patent your anti gravity machine now.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 07, 2018, 10:50 pm
You'd need to define "physical entity" fairly carefully to make that claim watertight, and probably
lose the baby with the bathwater in the process.  To a semiconductor physicist holes are very real...
Yes, holes are real, in the sense that a hole in the ground is real.  If I try to set a flower pot on a "hole" it will not be supported, and I can fill it with water.  It's an absence of dirt defined by the dirt around it.  But, if I dig a hole next to it, and toss the dirt I dig up, into the previous hole, the hole will appear to have moved.  But did it?

I can conceive of a model where holes in the ground "move", and it may work for certain physical systems -- like, maybe, some sort of "outback whack-a-mole", or stop motion animation where the hole becomes a character.  But, the model falls apart if I actually try, on hands and knees, to shove the hole around the ground it's dug in.

If I try to actually move a hole in a crystal lattice--the lattice will shatter.  The hole doesn't move, but it's useful to conceive of a model of it moving.  But, that's all it is -- a model!  And any physicist is deluding him/herself if they believe holes actually move.  Believing models are real is a trap that even scientists fall into, and a trap that limits their thinking in a way that can hinder innovation.

And to make this crystal clear [pun?], I'm NOT debunking holes, I'm pointing out that the idea that holes actually move is a delusion, in the same way, anthropomorphising an android is delusional.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 07, 2018, 11:10 pm
You'd need to define "physical entity" fairly carefully to make that claim watertight, and probably
lose the baby with the bathwater in the process.  To a semiconductor physicist holes are very real...
Agreed. All these 'physical' things we see today appear to be formed by some forces (or whatever they call them which scientists probably don't know the origins of, or how they exist etc). Those forces (or something) somehow form (or give us the impression of) things/entities/objects that people are able to define through observation, or theory, or measurements etc...... what appears to be physical definable things, but are a result of 'forces' (or something, which themselves aren't understood in terms of what they are, where and why.) Eg.... these forces somehow combine to give impressions of 'electrons', 'holes', 'rocks', 'wood', 'atom', chemical 'molecules', electric/magnetic fields etc. So at the base of it.... if OP is talking about current, or charge flow..... it's sort of like talking about how the forces (probably in some matrix pattern across our universe) bans together to give the impression of an 'object' or some lumped things moving.

So...... as long as we define something clearly, and as long as we agree upon following particular definitions, then this helps to avoid issues with the communication.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 07, 2018, 11:46 pm
Agreed. All these 'physical' things we see today appear to be formed by some forces (or whatever they call them which scientists probably don't know the origins of, or they exist etc). Those forces ...<snip>
I wasn't saying holes are not real -- just that they don't really move.  But, I see my error. : I got my wording wrong. ;)
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 08, 2018, 12:11 am
Quote
I wasn't saying holes are not real -- just that they don't really move.
Of course they move, how else can they have a mean free path?
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 12:26 am
Of course they move, how else can they have a mean free path?
What, exactly, is moving?
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 08, 2018, 12:31 am
What, exactly, is moving?
The hole.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 12:47 am
The hole.
You're funny!
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 08, 2018, 10:48 am
I am also a physicist.
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 08, 2018, 11:02 am
I think you're confusing current flow in a conductor with current flow in a semiconductor.
  • Conductor: Movement of free electrons [a property of metals].
  • Semiconductor: More like what you're describing [a property of specially doped semimetals or more exotic alloys].


Yes. You are absolutely correct, I am speaking of a semiconductor. Of course, nearly every (non-super)conductor has some semiconductor characteristic. "Free" electrons are not perfectly mobile in a conductance band. For a conductance band is not a band at all, but closely overlapping high energy orbitals in a close packed array of atoms. The electrons need to jockey for position, because, although there are a lot of states, Pauli still applies.  In a piece of wire the mass of the electrons crawls along many thousand times slower than the movement of the charge, aka the current.

It's within this jumble of buzzing electrons that the holes exist - they are unoccupied orbitals.

Title: Re: Which direction does current flow?
Post by: GolamMostafa on Jun 08, 2018, 11:09 am
Quote
Chris is right about that. Eg.... a parallel plate capacitor. During the charging and discharging stages, the electrons don't move across the 'gap' from one side of the plate to the other when a voltage source is applied across the two plates.
There is no electron movement across the plates of a capacitor. When an AC signal is impressed across the capacitor, there is the flow of electrical energy. Flow of electrical energy involves the flow of current. This is Maxwell who introduced the concept of displacement current which flows across the capacitor plates due to change in electric flux to enable energy flow. (it = ic + id = conduction current due to carrier + displacement current due to electric flux change)
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 08, 2018, 11:10 am
The hole.
I think he was asking for a definition of what "moving" really means rather than for the thing that is moving.
Title: Re: Which direction does current flow?
Post by: RuneJ on Jun 08, 2018, 12:45 pm
All this talk of holes or absences of electrons moving reminds me of a nice Terry Pratchett quote:
Quote
Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.
:)
Title: Re: Which direction does current flow?
Post by: terryking228 on Jun 08, 2018, 02:05 pm
I love it when we take a subject like this and run with it...

I see it like the small trees I just planted in my yard.

The holes we are talking about are an atom in a lattice that has the LACK of one electron.

If there are 3 holes in a row, and the first one acquires an electron, there are 2 'holes'.

If the electron moves from hole 1 to hole 2, the hole 1 reappears.

If I put a tree temporarily in my first hole, there are two holes left.

If I move the tree to the center hole, there are two holes left. 

So I can propagate holes. Trees can drift in one direction, and holes (the LACK of a tree) can propagate in the other direction.

OK, enough... I gotta go water those trees.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 05:07 pm
The hole.
I still maintain that the hole doesn't "move".  Holes merely appear and disappear--as electrons occupy/vacate orbitals.  Movement is a "useful delusion", in the same way cinema is.  The appearance of movement on the screen is a phantom created by the mind.  And, in fact, the so called movement of holes isn't even seen.  That's why I used the word "delusion" in association with hole movement, and illusion in terms of movie movement.  

In fact, isn't it true that there isn't, even, a physical hole--as in some stationary pit surrounded by boundary defining electrons?  I mean, in reality, it's just one less probability cloud, around the nucleus of an atom, right?  So, to call that a hole, is even more delusional, right?  And by delusional, I mean, a model, and not an actual thing.  A useful delusion.

So, hole, is a model for a missing electron cloud -- which doesn't really resemble a hole.  And, any movement of this phantom entity, is only conceptional.  In an electric field, they do seem to move, but not really -- but, it's useful to think of it that way.

And, consider this: locking yourself into a way of thinking, based on an accepted model, makes it difficult to advance the field.  Einstein was able to discard models and think beyond them.  Because he was able to think beyond Newtonian Physics, he knocked Physics on its ear.  The history of the conceptualization of the atom is another good example.  If physicists had decided that the plumb pudding model was the end-all-be-all, science would not have found its way to orbitals and the to the current, very strange, model of the atom -- and it's still a model!

But, I'm not a Physicist.  :P
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 08, 2018, 05:25 pm
So I can propagate holes. Trees can drift in one direction, and holes (the LACK of a tree) can propagate in the other direction.
The holes themselves are still pretty firmly in place... it's just that one appears when you take out the tree, and it disappears when the tree is placed in one. The location of where a hole is moves. The hole itself doesn't.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 05:41 pm
The location of where a hole is moves.
How do you know it's the same hole?
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 08, 2018, 05:44 pm
How do you know it's the same hole?
It just has to be as it's not the same location, right? Unless it's a black hole, but then that's most likely because someone dropped a can of paint.

Aaargh!
Title: Re: Which direction does current flow?
Post by: GolamMostafa on Jun 08, 2018, 06:34 pm
Quote
The absence of the electron in the covalent bond is represented by a small circle, and such an incomplete covalent bond is called hole. The importance of the hole is that it may serve as a carrier of electricity comparable in effectiveness to the free electron. The mechanism by which a hole contributes to the conductivity is qualitatively as follows: When a bond is incomplete so that a hole exists, it is relatively easy for a valence electron in a neighboring atom to leave its covalent bond to fill this hole. An electron moving from a bond to fill a hole leaves a hole inits initial position. Hence the hole effectively moves in the direction opposite to that of electron. This hole, in its new position, may now be filled by an electron from another covalent bond, and the hole will correspondingly move one more step in the direction opposite to the motion of the electron.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 06:37 pm
It just has to be as it's not the same location, right? Unless it's a black hole, but then that's most likely because someone dropped a can of paint.

Aaargh!
What if electrons leapfrog atoms, and populate holes more than one atom away [leaving the adjacent hole--the one expected to catch that wayward electron--to be filled by another leapfrogging electron]?  Or, maybe they don't always travel along the same "level" but can, also, jockey for positions on different three-dimensional levels.  Is it really known if electrons always leap to holes that are exactly adjacent?  How do you maintain the identities of holes that leap around in such an unpredictable manner?  If you point to an adjacent hole and say you know it's previous location, you would be wrong some [or even most] of the time.
 
And, what if, in a Universe where this is true, understanding this subtality of movement, and how to control it, leads to the next fulfillment of Moore's Law?

Just an example of how getting too ensconced  in a model can cloud creative thinking--and ultimately: progress.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 08, 2018, 06:42 pm
Quote from: GolamMostafa date=1528410370
The absence of the electron in the covalent bond is represented by a small circle, and such an incomplete covalent bond is called hole. The importance of the hole is that it may serve as a carrier of electricity comparable in effectiveness to the free electron. The mechanism by which a hole contributes to the conductivity is qualitatively as follows: When a bond is incomplete so that a hole exists, it is relatively easy for a valence electron in a neighboring atom to leave its covalent bond to fill this hole. An electron moving from a bond to fill a hole leaves a hole inits initial position. Hence the hole effectively moves in the direction opposite to that of electron. This hole, in its new position, may now be filled by an electron from another covalent bond, and the hole will correspondingly move one more step in the direction opposite to the motion of the electron.
That's a nice description of the currently accepted model.
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 08, 2018, 06:51 pm
Then there's also the problem of an electron moving/leapfrogging/whatever. According to quantum physics, what we call "the location of the electron" is just the place where (it is most likely to)(most of it can) be found, but in reality it supposedly can be just about anywhere in the universe, and that preferably at the same time. So even the "moving of an electron" is probably an incorrect description.
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 08, 2018, 09:14 pm
A hole has a mass you can weigh it.
A hole can move in a substrate. It has velocity.
A hole can collide with other holes and bounce off them.

All these "missing" electron stories are just that, a convenience fiction for those who don't want to go too deep into the theory. Holes are real.
Title: Re: Which direction does current flow?
Post by: tinman13kup on Jun 08, 2018, 11:35 pm
I see a bunch of people who really got deep into this subject. I never learned too much about it, but I do know this-
  out of holes, electrons, and current-current is the one that will really get your attention
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 08, 2018, 11:47 pm
I see a bunch of people who really got deep into this subject. I never learned too much about it, but I do know this-
  out of holes, electrons, and current-current is the one that will really get your attention
I think the main thing is just to consider (as these scientists appear to be suggesting) .... is to think of the universe as some kind of system .... some matrix, and for some unknown reason (simply unknown), there are building blocks.... or more like building 'forces'. So some combinations of these building 'forces' get together (somehow) to form things like fields, protons, quarks, sparks, neutrinos, electrons, photons, atoms, etc. The atoms and molecules appear to be what we 'define' as solid. All these physical 'stuff' is defined by humans --- we 'sense' them, or 'measure' them, or predict them ....and we define them.

In this universe, people don't even know what the origins are..... of electrons, holes, fields, etc. They just know how to define and measure these 'quantities'/'entities' that they see or sense, and know how to make use of them ----- ie. do things with them if they can.

So, as long as something like 'holes' is defined, then just treat holes as yet another physics defined 'thing'. And just use current as whatever it is defined to be by physicists....and use current as it is shown in circuit theory (ie. adopt a convention, and go for it).

As for OP's question of which direction does current flow..... if just focusing on basic circuit theory, just go with most circuit theory text books and use 'conventional' current flow ----- and use a sign convention for voltage, current and power .... aka 'passive sign convention'. You would only get into the hole and electron discussion when entering the physics area.
Title: Re: Which direction does current flow?
Post by: tinman13kup on Jun 09, 2018, 12:20 am
Oh, I know our hobby end of electronics doesn't even scratch the surface of the big picture when it comes to physics. I just have a suspicion the Grumpy_Mike used to be known as Happy_Mike before college.
Title: Re: Which direction does current flow?
Post by: terryking228 on Jun 09, 2018, 01:01 am
Quote
when it comes to physics. I just have a suspicion the Grumpy_Mike used to be known as Happy_Mike before college.
I was only temporarily a  Uconn Physics Major (1958) , but I was only Grumpy because they wouldn't Frickin' let me TOUCH anything. "When you are a Senior, you can do a Project"..  Grr....  So I dropped out...

NOW: Every entering Engineering and Computer Science student goes to the Bookstore and BUYS MY KIT (https://arduino-info.wikispaces.com/YourDuinoEngStarter)!  Barnes and Noble just ordered 700 for the Uconn bookstore.   OMG, it took 60 years to get my Revenge!  

I am so happy that times have changed and it's understood that early hands-on experience is vital to getting kids really involved with things that are INVISIBLE.  Like my kit says, "UH-OH! Electricity is INVISIBLE"..  

Mike, please explain (Yeah, I know... I didn't major in Physics..) how a "Hole" has measureable weight.  Is it the mass of a (for example Silicon) atom, minus the mass of an electron??  Hmmm....
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 09, 2018, 06:13 pm
A hole has a mass you can weigh it.
A hole can move in a substrate. It has velocity.
A hole can collide with other holes and bounce off them.

All these "missing" electron stories are just that, a convenience fiction for those who don't want to go too deep into the theory. Holes are real.
Science is just another mythology. Probably a better informed mythology than most, but when you get down to brass tacks, no one really knows what it all really is.  Any "scientist" who thinks otherwise, is living, and thinking in a deluded state. 
Title: Re: Which direction does current flow?
Post by: Johan_Ha on Jun 09, 2018, 08:58 pm
Quote
no one really knows what it all really is.
A statement like this always makes me want to ask what it would mean or what it would take to really know what it all really is. To make a statement like that requires that you know. So by all means, tell us.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 09, 2018, 10:30 pm
Science is about gathering information ... observations... via our senses and measurements and technology etc.... and recording/documenting those observations.... and then attempting to develop tools... mathematics and formulae and systems (definitions) etc. that not only allow observations to be explained in terms what is so-far known or built on.... but also to be able to utilise the knowledge gained from the relationships found or developed in the science.... applied science/engineering etc.... for technological advancement.

In science, we know that there are many things that we don't understand or know about the universe's behaviour or properties or origins etc. It's an effort toward understanding more, expanding our knowledge about the universe -- based on 'scientific' methods... and the definition of scientific is quite well defined....dictionary.

But .... this should really be discussed in the all-subjects area.

The OP is asking about which direction 'electrons' flow. Maybe the best answer is.... ignore electrons unless it becomes a physics discussion.... or if it becomes a semi-conductor physics/electronics discussion... which probably doesn't fall under the 'general electronics' category. Although, I can understand that 'electronics' itself contains the word 'electron'.
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 10, 2018, 12:07 am
Quote
OMG, it took 60 years to get my Revenge
Yes but it was sweet wasn't it.  :)

Quote
Science is just another mythology. Probably a better informed mythology than most, but when you get down to brass tacks, no one really knows what it all really is.
I can see why you say that, but I would not say just another, I would say it is "the" mythology because it is consistent and can be proven through mathematics. If the maths doesn't work then it is rejected or at least worked arround. Now what that maths mean in Physical terms is open to interpretation and we are hampered basically by lack of imagination when trying to describe phenomenon that has no analogue in the world we perceive.

Take an electron's relationship with a nucleus, we know a few basic facts, like there is a lot of space between them and electrons carry discrete energy levels but the "model " of an orbit and shells is convenient but wrong. And so are all the other things we can draw an analogue to in the world we piecieve.

Quote
how a "Hole" has measureable weight.
It just drops out of the maths when you describe what it is doing and how it works. I don't think any one has actually measured it but interestingly enough it does mean that an electron has a negitave mass, which just means the way it will react to a gravational field. And as we don't know what gravity actually is then that is all we can say about it.

Having been in both fields I can say that physicists don't think of electron flow as such unless they specifically need it, they all use conventional current. And for electronics engineered it doesn't matter one jot what way the current flows either convention will work as long as you are consistent. I think that is the basic misunderstanding of a beginner they think it matters because in a circuit the electricity will be used up by the first component it enters. Which is of course a noncense.
Title: Re: Which direction does current flow?
Post by: GolamMostafa on Jun 10, 2018, 02:47 am
A hole has a mass you can weigh it.
Quote
It is found that, when quantum mechanics is used to specify the motion within the crystal of n electron or hole on which an external field is applied, it is possible to treat the hole and electron as imaginary classical particles with effective masses mp and mn respectively. The approximation is valid that the externally applied fields are much weaker than the internal periodic fields produced by the lattice structure. In a perfect crystal these imaginary particles respond only to the external fields.

In conclusion, then, the effective-mas approximation removes the quantum features of the problem and allows us to use newton's laws to determine the effect of external forces on the elctrons and holes within the crystal.
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In general, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me(mp) (9.11×10−31 kg).
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 10, 2018, 02:57 am
A statement like this always makes me want to ask what it would mean or what it would take to really know what it all really is. To make a statement like that requires that you know. So by all means, tell us.
A while back, Bob Williams pointed the Hubble Space Telescope at a part of the sky that appeared empty.  Turns out, it wasn't so empty.  But, before that happened, I could have said, "Nobody knows what is beyond the farthest observable galaxy."  And, I wouldn't have know, myself.
So, I'm not sure what you're talking about.
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 10, 2018, 03:11 am
Science is just another mythology. ...
No, science is NOT a mythology! Science is a methodology, not a set of beliefs.

A mythology is a dogmatic explanation for observations. Science is a series of actions about asking and developing answers to questions. Mythologies have the explanation already pre-set.

Scientists spend their time disproving beliefs, not the other way around.
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 10, 2018, 06:41 am
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Scientists spend their time disproving beliefs,
Quite right.

Well trying to at least. When they can't the conclude that they must be right. Then it is on to experimentation to see if they can spot what is predicted, like the recent discovery of gravational waves. They were predicted from the maths about 100 years ago.
Title: Re: Which direction does current flow?
Post by: Johan_Ha on Jun 10, 2018, 07:41 am
When we have a spark jumping over a gap, it jumps from the negative electrode to the positive electrode, right? And the direction is even visible, right? That is one thing, where the actual physical direction of "matter" in an electrical current might have a meaning.

A spark plug lits up 40 times per second at 5000 rpm. Could it be that there's an advantage when the spark starts at the ground electrode instead of the firing pin? The ground electrode is nearer the centre of the combustion chamber.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 10, 2018, 07:53 am
No, science is NOT a mythology!
It is, when scientists talk like current "knowledge" is fact.  Facts that often become yesterday's can-you-believe-we-used-to-think-that?  But, then, I would argue that they are not the best scientists.  

And doesn't Quantum mechanics give us president to wonder if things don't go all wonky when no one is looking?  We receive clues about the nature of reality from our senses, and some very smart people have made it possible to "see" beyond the range of our senses.  But, what if there are things out there that don't even come close to anything we perceive?  How would we even begin to ponder that?  It's entirely possible that what we take for "reality" is just something that was made up for us, to keep us entertained.  And all Math and Science do is piece together the delusion.
Is it not suspect, that we are measuring the Universe with the same stuff the Universe is made of?  A bunch of atoms trying to work out what atoms are.  Kind of like a ruler trying to measure itself, or a glass of water trying to drink [or grok] itself.
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 10, 2018, 08:49 am
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It's entirely possible that what we take for "reality" is just something that was made up for us, to keep us entertained.
Well not so much entertained as allow us to survive and evolve in the world we find ourselves in.

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And all Math and Science do is piece together the delusion.
No not at all. Maths is the way the universe can be described in a consistent and correct manner. There is nothing delusional about mathematics.

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It is, when scientists talk like current "knowledge" is fact.
Scientists never do this only slack jawed journalists, politicians and pseudo scientists do this.

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Facts that often become yesterday's can-you-believe-we-used-to-think-that?
This is a line that pseudo scientists use to justify their crackpot theories.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 10, 2018, 10:17 am
Is it not suspect, that we are measuring the Universe with the same stuff the Universe is made of?  A bunch of atoms trying to work out what atoms are.  Kind of like a ruler trying to measure itself, or a glass of water trying to drink [or grok] itself.
It's not suspect if nobody actually knows how far we can go and what the universe has to offer. People are making measurements of quantities that people (ie. us) define(d). Many of these quantities and relations we came up with have certainly been useful .... it gave us internet and Arduino.

Yeah.... but we should take this to the general discussions area..... as it has gotten away from the OP's question.
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 10, 2018, 10:25 am
...
pseudo scientists ...
Would that be those on retainer by Fox News or employed by a pharmaceutical development company?
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 10, 2018, 11:12 am
Would that be those on retainer by Fox News or employed by a pharmaceutical development company?
Those, plus all of those Donald Trump appoints to his "science" bodies - I heard something like the EPD has been ordered to produce research that proves that global warming is not caused by people... I've always been taught that the research comes first, and that the conclusion is a result of what has been found in the research...
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 10, 2018, 05:18 pm
We try not to think about that.
Title: Re: Which direction does current flow?
Post by: ted on Jun 10, 2018, 05:26 pm
Thread name is about current not electrons, holes ....
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 10, 2018, 06:00 pm
Thread name is about current not electrons, holes ....
Water current?
Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 10, 2018, 06:24 pm
Thread name is about current not electrons, holes ....
To be able to answer the question "in which direction does current flow" you first have to figure out what current actually IS.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 10, 2018, 06:28 pm
Yeah.... but we should take this to the general discussions area..... as it has gotten away from the OP's question.
Yeah, the OP must be thinking "geeze, I'm sure glad I didn't ask something more complex, like how current flow relates to magnetism!"
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 10, 2018, 06:31 pm
Water current?
Context is the key, here.  Electronics related forum -- therefore we can assume electronics related question.

Title: Re: Which direction does current flow?
Post by: wvmarle on Jun 10, 2018, 06:37 pm
Then how about current in water vs. current in metals? Electric charge is transported very differently in the two media.
Title: Re: Which direction does current flow?
Post by: Johan_Ha on Jun 10, 2018, 08:14 pm
Is the speed of an electric signal the same in water and metal? Not very far from the speed of light? The electric current is not that different, is it? Water only has a much higher resistance and depends highly on how much stuff there is in water forming ions.
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 10, 2018, 09:14 pm
Context is the key, here.  Electronics related forum -- therefore we can assume electronics related question.


Yeah, I know. I was reacting to the statement that this thread was about current, not electrons or holes. But electrical current is movement of electrons and holes. Electrons flow from negative towards positive charge, while holes flow in the opposite direction. Ya can't speak of current without mentioning electrons and holes, as they are the thing flowing.
Title: Re: Which direction does current flow?
Post by: GolamMostafa on Jun 10, 2018, 10:01 pm
Transfer of Electrical Energy is a reality. The transfer takes place via the movement of electrons in metals is a concept supported by mathematical reasoning, and it is studied in Electrical Engineering.

Electronic Engineering deals with the movement of electrons and holes in semiconductor.  Signal processing takes place via the On/OFF conditions of the transistors is a reality. These ON/OFF conditions of the transistors happen due to accumulation/removal of charges (due to electrons/holes) in the base region of a transistor is a concept established by rigorous mathematical reasoning.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 10, 2018, 11:35 pm
If they want to get into current and electron movement relationship in classical conductors, then they need to read up on electron scattering, where they'll encounter words like 'average', 'net' etc, and discussions on collisions, and 'electrons' moving in various directions in applied electric fields.
Title: Re: Which direction does current flow?
Post by: pwillard on Jun 11, 2018, 07:00 pm
Or you just use the "filled pipe" concept.  Electrons in a WIRE is like a pipe full of something... let's say Jello.  If you "transfer" a charge in (or add some jello to the pipe) some will now fall out the other side... It won't be the EXACT item you pushed in... but a TRANSFER gets created that moves its way through.  The pipe or conductor remains essentially the same even though there was some "flow" or "transfer" that occurred.

So in my opinion... things "moving" isn't as exact as saying that things are "transferring".

Note: I'm not any sort of a scientist but I also "poo poo" all the commentary that says, scientists lock on to what they call facts and are immovable about them.  If there are enough data points and tangible proof, a scientist would agree that "clouds are made of fairies", but until that data comes in... they will all agree that clouds are made of water vapor.  This is what they figured out a while ago... but some would be willing revisit that conclusion if new data gets presented and can be independently confirmed by others.  What they won't do is agree that clouds are fairies without a source of new data.
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 12, 2018, 02:40 am
If there are enough data points and tangible proof, a scientist would agree that "clouds are made of fairies", but until that data comes in... they will all agree that clouds are made of water vapor.
Most of the replies to my comments indicate a misunderstanding of what I'm saying.  But, I'm not surprised. It's a difficult thing to convey.  For instance, I'm not saying, necessarily, that those in the science fields, tend to be "scientists [who] lock on to what they call facts and are immovable about them".  Only that they tend to shoot down things that are not proven.  For instance, can a scientist really, credibly say, there's no such thing as telepathy, or precognition, or ghosts, or fairy dust, or...?  Have they proven these thing don't exist?  Sure, they can say that statistically the likelihood is unlikely.  But to emphatically disallow such things, is unscientific!

And, really, can we be sure reality remains the way it has appeared, when we aren't looking?  Isn't it possible that reality intentionally behaves a certain way when an experiment is performed--i.e. that there is some intelligence, intentionally tweaking the experiment so the result meets some arcane agenda?  And, if we're all being deluded, then isn't science merely a study of that delusion--without awareness of the delusive quality.  Sure, the math is valid--as applied to the delusion [i.e. it describes the delusion very well].  I mean, if it's all a delusion, then it has demonstrated a high degree of consistency--unless your weird Uncle Steve, who claims to see a different reality, is the one on the right track.

Why is this even worth considering?  Maybe it's not.  But, I've had my share of experiences... empirical, yes, but so compelling as to defy the usual, science based explanations.  I probably can't prove it.  But, I've "seen" enough to wonder.  So, all I'm saying is, consider a world beyond the perceived world, where plays a greater physics.  Quantum mechanics is just the beginning.  There is more to be discovered, and science will get there, if it removes the stick it has up it's butt.
Title: Re: Which direction does current flow?
Post by: Southpark on Jun 12, 2018, 03:02 am
Why is this even worth considering?  Maybe it's not.  But, I've had my share of experiences... empirical, yes, but so compelling as to defy the usual, science based explanations.  I probably can't prove it.  But, I've "seen" enough to wonder.  So, all I'm saying is, consider a world beyond the perceived world, where plays a greater physics.  Quantum mechanics is just the beginning.  There is more to be discovered, and science will get there, if it removes the stick it has up it's butt.
The thing here is ..... a lot of these perceptions that you were talking about appear to be conjured up in your own mind. You just have to remember, that in most relatively large populations - there are variations. Some people have tendencies and behaviours you describe. Others do not. This just means, regardless of 'scientists' or whatever group we're talking about, not every 'scientist' has the features or characteristics you described. The comment about 'removing the stick' is based on your own conjured view (of science..... what you think it is). Science is basically about gaining knowledge and building up on it, and applying it to further our knowledge, or to further understand the behaviour of the universe, or to benefit ourselves. Sure, there are always negative impacts - like scientific outcomes or developments or applications can be turned against people and animals and environments. We could say it is still a part of 'nature'.

I reckon the OP's question about current flow direction has been thoroughly addressed by the members. So perhaps time for time-out on this one?
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 12, 2018, 09:40 pm
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For instance, can a scientist really, credibly say, there's no such thing as telepathy, or precognition, or ghosts, or fairy dust
Well ghosts, if they existed, would violate the laws of thermodynamics so they can not exist.

Precognition would imply some form of time travel so there is no mechanism for that and telepathy has yet to be demonstrated although it remains a possibility.
Title: Re: Which direction does current flow?
Post by: Johan_Ha on Jun 12, 2018, 10:24 pm
Telepathy, precognition, ghosts, fairy dust... why are the examples always about things that are as far as possible from reason, from the world of myths? What does even fairy dust mean?
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 13, 2018, 01:35 am
Telepathy, precognition, ghosts, fairy dust... why are the examples always about things that are as far as possible from reason, from the world of myths? What does even fairy dust mean?
Youthful folly?
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 13, 2018, 08:01 am
Reminds me of a lecture where the lecturer said, "if anyone believes in telekinesis please raise my hand ".
Title: Re: Which direction does current flow?
Post by: polymorph on Jun 13, 2018, 06:20 pm
And, to more properly answer the actual OP question: Actual physical direction of current flow depends on the "charge carrier" involved:
  • Electrons, being negatively charged, are repelled by negative potential.  Thus, they will flow from positive to negative, or from more positive to less positive.


Was this a test? Am I the only one who read this?
Title: Re: Which direction does current flow?
Post by: Johan_Ha on Jun 13, 2018, 09:15 pm
I missed it  :-[
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 14, 2018, 12:08 am
Was this a test? Am I the only one who read this?
Oops, got that wrong -- I'll correct it...
Title: Re: Which direction does current flow?
Post by: ChrisTenone on Jun 14, 2018, 11:25 am
I saw it, but figured it was just a typo. We know what you meant.
Title: Re: Which direction does current flow?
Post by: pwillard on Jun 14, 2018, 01:30 pm
I saw the backwards statement... it felt like a speed bump with a sign right after it that said, "carry on" (since the second part of the sentence clearly showed they knew what they were saying).

But again... unless you are designing semiconductors, it's OK to just use the conventional flow concept because it's not critical to know which way... just that it "does" or "does not" ( and accept that MOSFET people are anti-social --  I mean non-conventional).
Title: Re: Which direction does current flow?
Post by: polymorph on Jun 14, 2018, 06:22 pm
I saw it, but figured it was just a typo. We know what you meant.
Sure, but then someone who doesn't know comes along and reads it. Of course it is a typo, but why not fix it?
Title: Re: Which direction does current flow?
Post by: ReverseEMF on Jun 15, 2018, 07:29 am
Sure, but then someone who doesn't know comes along and reads it. Of course it is a typo, but why not fix it?
I did.
Title: Re: Which direction does current flow?
Post by: ted on Jun 15, 2018, 09:17 am
How fast does current flow ?
Already 6 Pages in one  week.
Title: Re: Which direction does current flow?
Post by: Grumpy_Mike on Jun 15, 2018, 10:40 am
The actual charge carriers only go at about 30 MPH.

How fast does current flow ?
Already 6 Pages in one  week.
:)
Title: Re: Which direction does current flow?
Post by: MarkT on Jun 15, 2018, 03:06 pm
On average, that is.  Typical instantious speeds for electrons in metals are > 1000km/s !

In fact 30mph is a going to rapidly heat most metals, a few mm/s is common for drift
velocities in everyday wiring.
Title: Re: Which direction does current flow?
Post by: ted on Jun 15, 2018, 03:42 pm
Electromagnetic waves propagate in vacuum at a maximum speed of 299,792,458 meters per second . For a 12-gauge copper wire carrying a 10-ampere DC current, the speed of electric current (average electron drift velocity) is about 80 centimeters per hour or about 0.0002 meters per second.

So for 1 week = 6 pages = 13.44km = turtle