Electron flow vs. current flow

by Stephanie Chasteen on February 27, 2009

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 positive charge, like you say.  But we define electric current to be the opposite direction of electron flow.

There’s some good history on why it’s defined this way, but I’m too busy to find it right now — if someone has a good link, stick it in the comments, thanks!

UPDATE 4/27

Here’s a relevant comic from xkcd

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{ 57 comments… read them below or add one }

avatar neha November 27, 2012 at 1:31 pm

in circuit electron flow -to+ but in cell electron flow +to-

avatar Mark December 11, 2012 at 11:03 am

from the article:
And electrons do get pulled towards the negative charge, like you say
should be
And electrons do get pulled towards the postitive charge, like you say

right

avatar Stephanie Chasteen December 11, 2012 at 8:01 pm

Thanks, Mark, for catching the typo!

avatar P.S. December 17, 2012 at 3:00 am

In books we have read that current flow opp to e- flow but actually why nd how it occurs!! ? plz some1 have answer inform me.. thanks.

avatar chris March 5, 2013 at 7:43 pm

My E&M prof cautioned us not say “current flow” since current is already a flow (J=nqv). What he told us to say is “charge flows” (since electrons dont move far in a metal). Which direction you choose, + or – is immaterial as long as you are consistent on the type of current you are talking about because in a semiconductor there are two currents to deal with, holes and electrons, which unlike the metal case, they are free to roam the whole crystal. These current directions are opposite to each, confusing isn’t it?

avatar john butler July 4, 2013 at 11:56 am

negitive should always go to positive….mankind should learn a leson

avatar Len Lehman July 18, 2013 at 3:18 am

Current Flow: the Final Lowdown

The amount of purely bogus but academically-backed misconceptions on this subject is truly sad. Let me help you try to set things straight for this subject. Electrons do the work. They flow from an abundance of electrons, the negative terminal, toward the more positive terminal which is devoid of any free electrons. This flow causes “voltage drops” across resistances in the path. Their polarity is going to always be more positive toward the positive terminal, which leads way too many to incorrectly assume that the charge flows from positive to negative, when it is actually the other way around. The “hole” in hole theory is merely an absence of an electron. There are not any subatomic particles called holes. Electron theory dictates that the subatomic particle that does the work in electronics is the electron, which happens to be negatively charged.
There is a subatomic particle that flows the other way, from positive to negative: the Positron. The only problem with generating Positrons is that they only occur in Antimatter. They might have some of that for a few microseconds inside the supercollider at Bern. Right now it’s kind of hard to get any of that stuff to sit still long enough to make a semiconductor out of it, but I can’t even dream of what we’ll be doing when we can do that! Until then, electrons do the work.

I learned electronics from the U.S.C.G. in the 1970′s, worked in electronics all my life, and taught electronics for over 5 years. We owe a lot to Nicola Tesla.

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