Benjamin Franklin may not be the first name to come to mind in a physics class—he's probably more at home in another section of this website, what with founding the United States and all. But in addition to his work as a Founding Father, in addition to being the wittiest person in any room he happened to grace with his presence, and in addition to charming the French ladies with his New World genius and rustic aphorisms and rockin' spectacles, Ben Franklin was one of the premier scientists of his generation.

The image of Ben standing on a Philadelphia roof during a lightning storm, kite in hand, is probably one you've seen before. It pretty much demonstrates how dedicated Franklin was to his experiments. It takes a dedicated scientist indeed to leave the laboratory and venture into the real world, let alone risk electrocution for his work. Franklin proved that lightning was electricity, charging a device called a Leyden jar with the discharge during a storm¹. Perhaps his most significant contribution to electromagnetism, however, is something Franklin got completely wrong—and is still backwards to this day. Scandalous.

Ben Franklin was the first scientist to propose the conservation of electric charge, writing "the Electrical Fire was not created by Friction, but collected [...] Equality is never destroyed, the Fire only circulating."² He nailed that one. But then he went on to describe the two types of electricity as positive and negative, and this is where some head slapping starts.

Franklin's insight was genius. Up until that point, everyone else had thought positive and negative charge were separate types of electricity, and it was Franklin who was first to say no, hold on, these are the same thing, the same way the front of a coin and the back of a coin are still both the same coin. Ben then hauled off and flipped that coin, calling one type of electricity positive and the other negative, without realizing that what he called positive was not the charge of an electron. (To be fair, the existence of something called an electron took about another century to even be theorized).

Why was this a mistake? Well, in an electric circuit, it's the electrons that flow around the wire. But because of Ben, our convention is to define current as the flow of positive charge. That means that current and electron flow go in opposite directions.

Whoops. Well, in the words of Franklin, "Wink at small faults; remember thou hast great ones." Guess we can forgive him for the wrong guess, seeing as he was kind of busy inventing electricity, a country, and the entire field of philately all at the same time.