Question about flow of electrons and electric current

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Why is the electric current in the opposite direction of the flow of electrons?

One may say: "Oh, because the electric current represents the flow of positive charges"...

Okay, but why don't the theory use the electric current representing the flow of negative charges?

I heard from a professor that it is because in the beginning of the study of electricity "they" used to think that the electric current was caused by the flow of positive charges... then later they realized that it was caused by the flow of electrons (in the solid conductors) and then to don't remake the theory and to don't need to rewrite everything that was writen, they defined electric current as the flow of positive charges... (this was done because the direction of the flow of electrons does not make different for calculation purposes)... is my professor right?

Thank you,
Rafael Andreatta


Homework Helper
I think it is due to convention. Usually things go from high to low. High would be considered positive. I am just guessing though.
Electricity was discovered long before anyone had any idea that electrons even existed.
No-one could tell which way it was flowing - in fact there was a big argument about whether it was one thing flowing one way or two things flowing both ways.
James Clerk Maxwell decided it was probably just one thing and made a guess which way it flowed - he got it wrong!

Here's the book he wrote. If you ignore all the complicated maths it's interesting to read how he thought about it."
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