| Electronics > Beginners |
| DC flow of electrons and things like diodes |
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| The_Welding_Library_Guy:
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 |
| Paul Moir:
Long ago before anyone knew the charge of an electron, it was assumed that they flowed from positive to negative. Since the symbols and the way of thinking of circuits were defined by this error, it stuck. This is commonly called "conventional current flow". The truth is the electrons go the other way, but for most purposes it's just easier to pretend they flow from positive to negative so the symbols and names make sense. (EDIT: ah, welding: it's pretty obvious which way the electrons are really flowing there.) |
| David Hess:
The *electron* current flows from negative to positive because we initially assumed electrons were positive. The junctions on schematics point along *conventional* current from positive to negative. |
| dmills:
Also while electrons are the charge carriers in METALLIC conductors, this is not true in other types... In molten Salts for example it is the ion that is the charge carrier and electrochemistry was and (to some extent) still is a **Major** user of power, so coming from that direction it is not at all clear that they really got it wrong (Or that it much matters which convention folks use). Current flow in semiconductors is "Complicated". Good textbooks in EE mention the charge on the electron being negative and then (outside the chapter on device physics) never mention it again, because unless you are doing semiconductor physics, particle beam, or plasma engineering it really does not matter. Regards, Dan. |
| Brumby:
--- Quote from: The_Welding_Library_Guy on February 01, 2019, 09:06:35 pm ---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. --- End quote --- Yes there is. You have mixed the two concepts of "Conventional current flow" and the directly opposite "electron flow". All circuit diagrams are drawn as "Conventional current flow", so looking at them with electron flow in mind will confuse you no end. Basic rule is - never look at a circuit with electron flow in mind - unless you KNOW you need to. (Which is rare.) |
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