Office for Mathematics, Science, and Technology Education
College of Education @ University of Illinois
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Direction of Current

When scientists were first working with electricity, they didn't know about the structure of an atom, with electrons moving around the outside and protons stuck in the middle. They did figure out that something, which they called "electric fluid," was moving from one place to another, but they didn't know what this "fluid" really was. They decided it would help to be able to talk about which direction this stuff was moving. They picked one side and called it "positive," saying that it had a lot of "electric fluid." They called the other side "negative," saying that it had less "electric fluid." Then they set about trying to measure the flow of this "fluid" from "positive" to "negative."

Eventually, they learned that what was really moving was electrons, which were moving from the side that had been named "negative" to the side that had been named "positive." Oops! It would be a nuisance to change all the names, so they just kept it the way it was. "Current" replaced "electric fluid" as the name for stuff that flows from positive to negative, and the electrons kept on going from negative to positive, just as they had been doing before we knew anything about them.

Find out why this isn't quite as backwards as it seems.

This applet was written by Lisa Denise Murphy at the University of Illinois. Early drafts were written in 1999. The current version was last revised in January of 2000. Permission is given for students and teachers to use this applet, provided acknowledgement is made of the source. Anyone interested in using this applet in connection with any published paper or commercial venture should please first consult the author. Thank you.

This page last revised January 19, 2000.


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