The geekgirl is going a little nutty over here, hence the silence on the posting front. I’ve got a good excuse — I’m getting married in about 10 days. So cut a girl some slack. 🙂 Fun facts — we’re getting married on 9/10/11 — which only happens 11 times in every 100 years, and the next two years (10/11/12, 11/12/13) are the only such dates for another 90-something years. How cool is that? Our officiant is my old mentor Paul Doherty from the Exploratorium, and he’s doing something involving liquid nitrogen for the pre-wedding BBQ, and reading from Richard Feynman for the ceremony. So, two weeks from now, I’ll be covalently bonded to my sweetheart. One friend put it, “you’ll be Mrs. Geekgirl.” Hmm, I think that actually makes my sweetie Mr. Geekgirl, doesn’t it? 🙂
So, because I’m a bit too crazed to write something new, I’m reposting an oldie but goodie, describing the difference between electron flow and current flow. The original post has a VERY rich string of comments — check it out for more on this confusing topic!
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
But *current* is the opposite direction. Left to right.
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.
Why are we cursed with this convention? Here’s a relevant comic from xkcd