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DC power + or -? Answered

I have looked at lots of Instructables and websites, but there is a 50/50 split that power flows positive to negative and negative to positive. Which is it? I use both, depending on the circuit I am building it is easier to build one way over the other (NPN and PNP Transistors usually) But I have heard that it used to be thought that positive flowed to negative but I have since heard that the new idea is that it flows negative to positive. I know that everything is supposed to flow from higher concentration (+) to lower (-) but we could have batteries labeled wrong so I don't know. Very confused.



Best Answer 8 years ago

BOTH answers are correct! Many years ago, in Benjamin Franklins time, they GUESSED WRONG that it flowed from positive to negative. So all schematics and publications show POSITIVE flow. But scientifically, it actually flows from negative to positive. Unless you are a SCIENTIST, you should ignore this fact! On a schematic diagram, we look at a DIODE symbol and it looks like a funnel. The POSITIVE current flows in the direction of the "funnel" or arrow. It was decided many years ago to just IGNORE the mistaken direction of current flow (in the electronics industry) because they didn't want to re-print all the books and schematics ever written. Thats what they told us in electronics classes back in 1979... framistan

I can't pick two best answers but yours helped alot too! Thanks so much!

Right. It doesn't actually matter, of course, since Maxwell's equations are symmetric under charge-sign inversion. The electrons (negatively charged) do flow from the "-" label to the "+" label, while the "hole current" (as Seandogue labels it) flows from "+" to "-" as you'd naively expect.

...if you're going to be really picky, in the direction of majority carrier flow, AFAIR.


8 years ago

It flows from negative to positive. (think an LED, the anode and the cathode)

Yes but it goes in the same way which ever way the current is flowing. The arrow is either pointing in the direction it goes or doesn't go. The power could be flowing the other way through the LED (positive to negative) and the negative to positive way only works because the diode is placed in the circuit the same way. This isn't a simple black and white answer. Can you see the electricity flowing - to + through the LED? No, therefore since we can not see it we can't assume it flows that direction. It could flow + to - and still work as long as it is placed in the circuit the same direction. Maybe the diode is made that way, the arrow points the direction the current can flow, and since it is in the circuit the same direction we can think that it flows either way.