By my understanding their charge could have been called positive, and the charge of the proton and positron called negative. What are the historical reasons for this?


When they discovered electricity they were studying electric current. They called this a positive flow of charge, because it's in the direction of the current that they saw.

When they discovered the electron they found that it was moving opposite to the previously determined "positive" flow, therefore calling it negative.

When they discovered the proton they realized that it's attracted to electrons. Since electrons are "negative" they called protons "positive".

They're arbitrary naming conventions that have nothing to do with any actual physical properties of the particles.

You could switch them and as long as you maintain that switch on all your calculations then it all still works out.

  • $\begingroup$ Can you expand on that flow experiment? $\endgroup$ – Euphorbium Dec 30 '17 at 6:09
  • $\begingroup$ In 1733 C F du Fay rubbed glass with silk causing them to stick. He proposed two different electric fluids which cancelled each other out called Vitreous and Resinous electricity. Ben Franklin proposed the one fluid theory. In the Leyton jar experiment he figured all of this "fluid" was in the glass and would transfer. He posited that having too much of this fluid was excess or positive, and too little was negative. Later when the electron was discovered it happened to be flowing in the direction of the negative so they called it negative. $\endgroup$ – Bigjoemonger Dec 30 '17 at 6:23
  • $\begingroup$ Hi Big Joe. If you edited this information into your answer, possibly with some supporting references, it would make the answer a lot better. $\endgroup$ – John Rennie Dec 30 '17 at 7:09

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