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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in circuit electron flow -to+ but in cell electron flow +to-
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
Thanks, Mark, for catching the typo!
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.
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?
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