Electronics > Beginners
DC flow of electrons and things like diodes
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IanB:

--- Quote from: The_Welding_Library_Guy on February 02, 2019, 10:25:10 pm ---So to be sure I understand. DC components are labeled backwards to complied with the ideal of conventional current flow essentially? So say I have a 1N4007 dioide in a circuit. I would design the circuit so that the stripe points from positive to negative thinking the stripe represents the blocking side (not sure the accutal erm for this). But in reality the blocking side is the oppoist side that's pointed towards positive?
--- End quote ---

DC components are not labeled backwards, they are labeled properly. Current flows in the direction of the arrow and is blocked the other way. That is why LEDs work, because current flows forward through them in the direction of the arrow, and they have a forward voltage drop which is positive.


--- Quote from: The_Welding_Library_Guy on February 02, 2019, 11:42:51 pm ---Yea I understand that. I knew coming in that designing circuits pos to neg works. That's why everything I have ever seen is la yes out that way. I was just try to figure out why my understanding of the what's going on in the conductor didn't match what I was doing in the real world. I was just making sure I understood what I was being told. I know this will most likely never have a practical implementation for me. Was just more of a curiosity
--- End quote ---

In the real world, current flows from positive to negative. If you measure it with an ammeter it will show a positive reading when it is flowing from the positive probe to the negative probe. If you pass current through a resistor there will be a positive voltage difference in the direction of current flow.

Keep always in mind that current flows from positive to negative, and circuits are laid out and arranged to reflect that. As long as you remember that and don't confuse yourself with other ideas you will be fine.
vk6zgo:

--- Quote from: IanB on February 03, 2019, 12:02:04 am ---
--- Quote from: The_Welding_Library_Guy on February 02, 2019, 10:25:10 pm ---So to be sure I understand. DC components are labeled backwards to complied with the ideal of conventional current flow essentially? So say I have a 1N4007 dioide in a circuit. I would design the circuit so that the stripe points from positive to negative thinking the stripe represents the blocking side (not sure the accutal erm for this). But in reality the blocking side is the oppoist side that's pointed towards positive?
--- End quote ---

DC components are not labeled backwards, they are labeled properly. Current flows in the direction of the arrow and is blocked the other way. That is why LEDs work, because current flows forward through them in the direction of the arrow, and they have a forward voltage drop which is positive.


--- Quote from: The_Welding_Library_Guy on February 02, 2019, 11:42:51 pm ---Yea I understand that. I knew coming in that designing circuits pos to neg works. That's why everything I have ever seen is la yes out that way. I was just try to figure out why my understanding of the what's going on in the conductor didn't match what I was doing in the real world. I was just making sure I understood what I was being told. I know this will most likely never have a practical implementation for me. Was just more of a curiosity
--- End quote ---

In the real world, current flows from positive to negative. If you measure it with an ammeter it will show a positive reading when it is flowing from the positive probe to the negative probe. If you pass current through a resistor there will be a positive voltage difference in the direction of current flow.

Keep always in mind that current flows from positive to negative, and circuits are laid out and arranged to reflect that. As long as you remember that and don't confuse yourself with other ideas you will be fine.

--- End quote ---

No, in the real, physical, world Electron Flow is how current works.

The existence of vacuum tubes is the most important supporting argument for Electron Flow.
Saying "We don't use them anymore, so it doesn't count" is about as effective as sticking your fingers in your ears & saying "La,La,La,La!"

Yes, Conventional Current Flow is a useful concept, & works almost everywhere, but it is a historical accident, & can't be twisted into anything else,.
In an effort to justify CCF some people (notably EEs) insist that you would have to multiply everything by minus 1 if using Electron Flow.
This seems to be rooted in an archaic concept that "positive is 'higher' in potential than negative" which is in reality, utter balderdash.

Electron Flow  causes exactly the same polarity voltage drops across resistors as CCF.

This is the beauty of the thing--- we use CCF happy in the knowledge that things like "Right Hand rules" work, & we don't have to invent "Left Hand rules" -- for most everything else, the two ideas are interchangeable.

If your advice is to use CCF for its convenience, & don't go down the path of having to make mental conversions every time, I would agree, but denying the existence of the real mechanism of current flow in conductors because it is "confusing" is pretty much saying that people don't have the intellectual capacity to understand two different ways of viewing things.

I, & my contemporaries had no problem with the two concepts, so why are younger people likely to become confused?

MrAl:

--- Quote from: The_Welding_Library_Guy on February 01, 2019, 09:06:35 pm ---So, I understand that in DC systems current flows from Neg to Pos but one thing that confuses me is how a circuit like the one below works then? If current flows from neg it shouldn't be able to flow throgh the LED unless is bypasses the breakdown voltage. But even then it shouldn't light the led. Right? I'm sure theirs something simple that i'm missing here so I would be very grateful if anyone could help me understand a bit better.

~Thanks

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Hi,

You can view the circuit in two ways, using conventional current or the drift flow of electrons.
The components we often see have their arrows pointing in the direction that conventional current would flow if it could flow.
You can usually just forget about 'electron' flow.

An interesting fact.  If you view a wire as a tube of electrons and narrow that down to just one electron width, if you leave out one electron and watch the electrons move from right to left, you will find that the 'hole' moves from left to right!
Look for a video on the web.
IanB:

--- Quote from: vk6zgo on February 03, 2019, 02:33:11 am ---No, in the real, physical, world Electron Flow is how current works.
--- End quote ---

Your advice is exactly why the OP is confused. If you want to spread confusion, this is the way to proceed.

And in fact, considering electron flow is not the right way to reason about current. The correct way is to consider current flow to be an accounting problem, where we account for charge transfer. For example, if I lend you $100, is that positive or negative? You might think it is positive in that your cash balance went up by $100, but it is also a negative as you have now acquired a debt. You have to consider that you owe me $100 so that counts as −$100 in your net worth.

The same it is with current. Current simply causes charge to be transferred from A to B. If A is down 100 coulombs then B is up 100 coulombs. It really doesn't matter whether it is electrons or pixies that transfer the charge. The accounting is the same. Increased charges are positive and decreased charges are negative.
Brumby:

--- Quote from: IanB on February 03, 2019, 03:09:22 am ---
--- Quote from: vk6zgo on February 03, 2019, 02:33:11 am ---No, in the real, physical, world Electron Flow is how current works.
--- End quote ---

Your advice is exactly why the OP is confused. If you want to spread confusion, this is the way to proceed.

--- End quote ---
I have to agree.


You can be very successful with contemporary electronics - design, construction, testing and repair - without ever knowing about electron flow, especially where thermionic devices are not involved.
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