Electron flow vs. current flow

by Stephanie Chasteen on June 30, 2012

I’ve written a previous post about how the direction of the flow of current in a circuit is opposite to the direction of electron flow in the circuit, due to historical anomalies.  A lot of people seem to get confused by this.  And I thought maybe this xkcd could help:

If only we could go back, that would avoid this whole confusion!

Here is the original post:

I just got this question from a teacher on Webconnect (which lets teachers ask science questions):

“In the past when I taught electricity I always understood that it flows from the negative terminal to the positive.   The CPO books and materials have the opposite – from positive to negative.  This doesn’t make sense to me in how you generate the flow of electrons, pulling to the opposite charge.  Is the book wrong or have I forgotten stuff? 8th grade teacher”

It depends on what you define as “electricity”.  Do you mean the flow of “electrons” or the flow of “current”?  Because, due to an unfortunate quirk of history, the direction of *current* flow is opposite to the direction of *electron* flow.  Take a moment and re-read that, because it’s not what you would expect.  If electrons are flowing to the right across this screen, then we say that current is flowing to the left.

So, let’s say that the left hand side of this screen is the positive terminal and the right hand side is the negative terminal

+                  -

*Electrons* will flow towards the opposite charge, as you say.  That’s which direction?  Right to left

<—-  electrons

But *current* is the opposite direction.  Left to right.

—-> current

So *current* does flow from positive to negative, like your books say.  And electrons do get pulled towards the negative charge, like you say.  But we define electric current to be the opposite direction of electron flow.

 

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