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How did the concept of positive and negative charge originate before the discovery of an electron? My question is related to the historical aspects.

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marked as duplicate by Conifold, Nick R, José Carlos Santos, Carl Witthoft, tox123 Jan 19 at 3:47

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In the 1700s it was established that materials (especially those that we now call 'electrical insulators) when rubbed with other suitable materials, could be divided into two groups. All the rubbed materials repelled materials in the same group, but attracted materials in the other group. Benjamin Franklin called the group containing glass rubbed with silk "positively charged" and the group containing amber (fossilised resin) rubbed with fur "negatively charged". [He didn't think of positive charge and negative charge as of equal status as we now do; rather he thought of negative charge as an absence of the real stuff: positive charge!]

The reason that we now say that an electron has a negative charge and the proton has a positive charge goes back to Franklin's arbitrary decision to say that glass rubbed with silk is positive and amber rubbed with silk is negative. If you hold a rubbed lump of glass near an electron beam it attracts the beam; if you hold a rubbed lump of amber near the beam it repels it!

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    $\begingroup$ A slight modification: originally people thought there were two fluids, and the various substances were in the two groups based on which fluid they had. Franklin's advance was to introduce and then demonstrate conclusively that only a single fluid was needed, and the effects were due to having too much or too little. $\endgroup$ – Maury Markowitz Jan 15 at 19:36
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    $\begingroup$ @Maury but that's not correct, since without the remaining positive charge, the negatively charged item would not be attracted to the other item. $\endgroup$ – Carl Witthoft Jan 16 at 13:03