567: Urgent Mission

Explain xkcd: It's 'cause you're dumb.
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Urgent Mission
Sure, we could stop dictators and pandemics, but we could also make the signs on every damn diagram make sense.
Title text: Sure, we could stop dictators and pandemics, but we could also make the signs on every damn diagram make sense.

Explanation

Benjamin Franklin was one of the Founding Fathers of the United States. Aside from uniting most of his country against Britain's heavy-handed rule, he was also an author, printer, musician, politician, postmaster, inventor, scientist, and diplomat. Some of his legacies include bifocals, the Franklin stove, an odometer for a horse-drawn carriage, the almanac, abolitionist ideals, and his image on the $100 bill. For the purposes of this comic, Franklin also created the lightning rod and discovered the fundamentals of electricity, such as positive and negative charges, as well as the conservation of electric charge.

When Franklin first wrote down his notes for electricity, he defined a positive charge as a charge caused by glass rubbing on silk, and a negative charge as a charge left when fur rubs on rubber. This definition for electrical charges still exists today, including in electrical diagrams (as the title text notes). The problem is that as our knowledge of electrical circuitry increased, we realized that the flow of a current, from positive to negative, is not how electrons move in a wire. Rather, it is how the absence of electrons moves in a wire. The flow of electrons themselves go from negative to positive terminals, which is not the first thought that comes to mind in terms of electrical concepts. It's a confusing concept to many fledgling engineers, and one that the time-traveler considers a greater priority. It also adds minus signs in a few physics formulas.

Transcript

[Cueball steps out of rift. Benjamin Franklin is sitting at his desk with quill and parchment.]
Cueball: Benjamin Franklin?
Franklin: Yes?
Cueball: I bring a message from the future! I don't have much time.
Franklin: What is it?
Cueball: The convention you're setting for electric charge is backward. The one left on glass by silk should be the negative charge.
We were going to use the time machine to prevent the robot apocalypse, but the guy who built it was an electrical engineer.
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Discussion

The explanation is backwards. Current is defined as the flow of *positive* charge, thus moving from positive to negative terminals. In most cases, the current is actually electrons, which are moving from the negative terminals to the positive. 72.45.165.98 16:48, 27 June 2013 (UTC)

Hopefully fixed. This was hard to write clearly. 108.162.219.223 01:43, 11 January 2014 (UTC)
I might be completely mistaken but I've thought that the reason why the positive and negative terminals are assigned as they are originated from observing the electric current passing through the solutions of salt. In the said solutions the current consists of the positively charged ions that get deposited onto the negative electrode, while the positive electrode slowly dissolves. This naturally makes one think that the electric current carries the charged particles from the positive to the negative electrode. Of course it might be that I've completely forgotten what I've been taught in school and gotten everything wrong. 108.162.246.5 01:50, 29 January 2014 (UTC)
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