If this next part is too confusing, just skip over it. I did want to let you know (for those of you who have spotted it already) that there’s a big problem with the positive test charge model we’ve been using. Well, it’s kind of a problem, but not really a big one once you get used to the idea.

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When we determined which one is the high and low potential (the plus and minus on a battery), we assumed that the test charge was positive. The particles that move charge through the wires are actually negatively, not positively, charged. We’ve been dealing with just positive charges so far, and now we’re going to mix things up a bit since electrons are in fact, negative. This means that current actually goes from the negative terminal to the positive terminal because that charge is being carried by electrons. Note that charge carriers don’t have to be electrons (they can also be positively charged or both traveling simultaneously in opposite directions!)

It was actually one of Ben Franklin’s not-so-great moments when he arbitrarily assigned the direction of electric current the way we think about it today, which is going from the positive to the negative terminal. Electrons actually move in  the opposite direction! BUT in the real world, we all think about current flowing from plus to minus (even though in reality its the opposite direction). Just file it away in your mind in case it ever comes up (which it probably won’t) that you would need to know the actual direction the electrons are moving in a circuit (which most people don’t need to know or care about).

Click here to go to your next lesson on learning about charge carriers!

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