Electron Flow vs Conventional Current Flow - So Confusing!

Thread Starter

TeslaTechie58

Joined Jan 22, 2019
3
Hello all, I've read, and read, and read posts about this topic but I'm still confused. As someone new to hobby electronics I'd like to get this concept straight in my head before moving on. I believe the source of part of my confusion is the fact that we're told that current can't flow the wrong way through a Diode (LED). Yet many of the schematics shown on the internet show electron flow through the pointed end of a Diode. I thought this was a no-no? This logic is what's confusing me, not the arbitrary sign convention. I have no problem with a sign convention as long as it's used consistently. My problem is thinking about electron flow and seeing schematics on the internet that seemingly shouldn't work at all. When people say that it doesn't matter which way the current is assumed to flow, this just further confuses me. It seems like it would absolutely have to matter in the design and placement of components! What am I missing here? Please help!
 

crutschow

Joined Mar 14, 2008
25,263
Conventional current flow assumes a positive charge carrier and is through a diode from anode to cathode (in direction of symbol arrow).
Electron flow through a diode uses a negative charge carrier and is from cathode to anode (opposite the direction of the symbol arrow).

So which ever you assume will be fine as long as you use the same assumption in the whole circuit.

What about that is confusing you?
 

wayneh

Joined Sep 9, 2010
16,399
Here we go! This one has been covered here ad nauseum so I won’t say much more except to address the diode question. A normal diode conducts (conventional, from plus to minus) current in the direction of the point of the triangle. A zener diode conducts in either direction if the reverse breakdown voltage is exceeded.
 

Thread Starter

TeslaTechie58

Joined Jan 22, 2019
3
Conventional current flow assumes a positive charge carrier and is through a diode from anode to cathode (in direction of symbol arrow).
Electron flow through a diode uses a negative charge carrier and is from cathode to anode (opposite the direction of the symbol arrow).

So which ever you assume will be fine as long as you use the same assumption in the whole circuit.

What about that is confusing you?
I'm now beginning to understand that it's ok to show current flowing into the point of the Diode. However, if electron flow reached an LED before going through a resistor which is shown on a schematic then wouldn't this result in burning out the LED? It seems to me that the order in which you place the components in the circuit has to matter. Take for instance the schematic below that I borrowed from a youTube Video. Electron flow would reach the Diode before reaching the resistor and would eventually cause the LED to fail, would it not?
upload_2019-1-22_19-58-18.png
 
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Norfindel

Joined Mar 6, 2008
326
Just use conventional direction, and nobody's harmed :p
Seriously, the arrows are drawn in the conventional direction in transistors, also. Not worth the effort to do the mental subtitution. We know that electrons actually flow the other way, but from a circuit design standpoint, it doesn't really change anything to draw it backwards.
 

crutschow

Joined Mar 14, 2008
25,263
It seems to me that the order in which you place the components in the circuit has to matter.
No.
In a series circuit the order of the components makes absolutely no difference in their operation.
It's the current flowing through the device multiplied by its voltage drop that determines its power dissipation, and that voltage drop does not change with order.
And, of course, the current has to be the same in all devices in series.

So that's what's been confusing you about the direction of the current, thinking it made a difference in the component function.
 

BR-549

Joined Sep 22, 2013
4,938
Current remains a real mystery. The flow of an electric charge is super fast.....but hardly goes anywhere.

It's sorta like space. Space is infinite, but has no volume.

As experience and knowledge grows many realize that it's the alignment of the charge that allows the fast transfer of power and information(signals). But we all relate and teach this transfer as charge flow(current).

So......the more you understand, the more complicated it seems to get.

We use positive charge flow for theory, analysis, spec and design, but a repair mechanic will use negative charge flow for troubleshooting.
 
Ben Franklin goofed. He got the sign wrong. For circuit analysis assume current "flows" from positive to negative. It doesn't really "flow". it's probably more like bumping cars.

MOST of the time it's doesn't matter which way you choose. In semiconductor physics it matters sometimes, so we invent "holes" and "electrons" to get us past that. It sometimes matters in chemistry.

Most bolts are lefty loosy, rightly tighty except the left handed threaded ones. We compensate for that. One car my parents owned had left handed bolts for the tires on one side and right handed on the other.

So......the more you understand, the more complicated it seems to get.
How true.

Hey, I successfully argued that the "wrong answer" was correct. Teach said, "Your not supposed to know that YET!".

If you move a wire on the earth it generates a current. Most people would say no it doesn't. Can you measure the resistance of a piece of paper?
I could at work. Are three resistors in series equivalent? The real answer is no, but the right answer most of the time is yes.
 

MrChips

Joined Oct 2, 2009
21,663
I was brought up using conventional current flow. It has not hindered me from being able to master and understand any number of electrical and electronic circuits. I think it is unfortunate that the AAC online tutorials use electron flow. I can live with that.

Just stick with one convention and you will get the hang of it in time.
 

crutschow

Joined Mar 14, 2008
25,263
Ben Franklin goofed. He got the sign wrong.
It wasn't a goof so much as a bad guess.
That's because there were no instruments available at the time to determine the sign of the charge carrier so he made an arbitrary designation for which he had a 50-50 chance of being right, which of course means he was wrong. ;)
The electron charge sign was shown much later by experiments, such as the Edison effect, where the charge would travel from the filament to a positively charged plate in the light bulb, but not to a negatively charged plate.
 

Sensacell

Joined Jun 19, 2012
2,587
Just ignore the idea of electron flow altogether... (unless you are involved in this existential discussion)

Diode and transistor symbols make perfect sense then, all is good.
 

dendad

Joined Feb 20, 2016
3,594
I like electron flow. In a diode, the way I look at it is electrons cannot flow when they hit the "wall" of the arrow head.
But, they can flow up the ramp of the arrow. The voltage required to do that is the diode drop.
 

jhovel

Joined Jul 9, 2016
31
I suggest you completely forget about ELECTRON flow. It is of no consequence that I've found. Their relative movement only serves to exchange atom-level charges and have bugger all to do with power or current. The 'Electicity' or current flows at close to speed of light, whereas the movement of electrons beweenatoms of copper or whatever is a LOT slower and serves no purpose in circuit design.
The only place it IS relevant is in the manufacture of integrated circuits where the distances of conductors is getting close to atomic dimensions....
 

nsaspook

Joined Aug 27, 2009
7,470
I suggest you completely forget about ELECTRON flow. It is of no consequence that I've found. Their relative movement only serves to exchange atom-level charges and have bugger all to do with power or current. The 'Electicity' or current flows at close to speed of light, whereas the movement of electrons beweenatoms of copper or whatever is a LOT slower and serves no purpose in circuit design.
The only place it IS relevant is in the manufacture of integrated circuits where the distances of conductors is getting close to atomic dimensions....
While I agree with most ('Electricity' and the movement of electrons are both slow (drift speed) in current electricity) of that, is it important to understand the circuit properties of electrons and protons in terms of charge. We do need to understand how charge carriers move and are separated even in simple circuits with passive components. Conventional current direction provides a sign convention that makes calculated charge movements consistent with most of the physical to mathematical relationships we see in engineering.

https://www.education.vic.gov.au/school/teachers/teachingresources/discipline/science/continuum/Pages/electriccircuit.aspx
 
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MrSoftware

Joined Oct 29, 2013
1,861
I'm now beginning to understand that it's ok to show current flowing into the point of the Diode. However, if electron flow reached an LED before going through a resistor which is shown on a schematic then wouldn't this result in burning out the LED? It seems to me that the order in which you place the components in the circuit has to matter. Take for instance the schematic below that I borrowed from a youTube Video. Electron flow would reach the Diode before reaching the resistor and would eventually cause the LED to fail, would it not?
View attachment 168475
Don't think of conductors as "empty" just because nothing is flowing. Think of a conductor as a straw full of water. When nothing is flowing, it's still full. When you put a drop in one end, a drop comes out the other end. It's not the same exact drop that you put in. As you keep putting drops in one end, eventually those drops will come out the other end. Wires/conductors are similar. They are full of electrons. So when the current starts flowing, and you put an electron in one side, another electron comes out the other side. If you could follow the first electron that you put it, some time (and a lot of other electrons) would pass before it comes out the other end. Electrons "propagate" through a conductor, and they move a lot slower than you would think. Here's a random article that addresses it, nothing special about this article other than it was a top google result.

As a result, passive components in series can go in any order and the behavior will be the same.
 

bwilliams60

Joined Nov 18, 2012
1,332
Being in automotive, I have been brought up in conventional theory and schematics as stated above, make sense. I tried to look at electron theory but it messes things up so I stick in my comfort zone. You just need to find the one that works for you, and make it your comfort zone.
 

Thread Starter

TeslaTechie58

Joined Jan 22, 2019
3
Don't think of conductors as "empty" just because nothing is flowing. Think of a conductor as a straw full of water. When nothing is flowing, it's still full. When you put a drop in one end, a drop comes out the other end. It's not the same exact drop that you put in. As you keep putting drops in one end, eventually those drops will come out the other end. Wires/conductors are similar. They are full of electrons. So when the current starts flowing, and you put an electron in one side, another electron comes out the other side. If you could follow the first electron that you put it, some time (and a lot of other electrons) would pass before it comes out the other end. Electrons "propagate" through a conductor, and they move a lot slower than you would think. Here's a random article that addresses it, nothing special about this article other than it was a top google result.

As a result, passive components in series can go in any order and the behavior will be the same.
I'm afraid I may not be stating my question clearly enough. It's not necessarily the order of the components, but the order of the components relative to the actual electron flow. If electron flow is opposite conventional flow I'm having trouble understanding how current makes it's way around the circuit (for instance, without being blocked by a Diode that's in the circuit. I guess I'm thinking like a technician/troubleshooter would have to think?
 

crutschow

Joined Mar 14, 2008
25,263
If electron flow is opposite conventional flow I'm having trouble understanding how current makes it's way around the circuit (for instance, without being blocked by a Diode that's in the circuit.
Because electron flow goes through a diode from cathode to anode (such as in a vacuum tube rectifier).
 
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