# Why is it that protons and electrons have exactly the same but opposite charge? [duplicate]

Possible Duplicate:
Why do electron and proton have the same but opposite electric charge?

Doesn't it seem very curious that one is an elementary particle and the other a subatomic particle yet the charge is exact same..

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Possible duplicate: physics.stackexchange.com/q/21753/2451 –  Qmechanic Aug 11 '12 at 23:51
Also related: physics.stackexchange.com/q/22921 –  dmckee Aug 12 '12 at 0:19

## marked as duplicate by Qmechanic♦, dmckee♦Aug 12 '12 at 0:18

It's due to the observed fact that all charges come in common multiples of the electron charge. The electron charge is the minimum charge an isolatable particle can have. Quarks have a charge of $1\over 3$$e$, so that could be considered the minimum charge. However, quarks are never found by themselves, due to a property called quark confinement. Instead, they are always found in either groups of three (baryons), or two (mesons). Any one of these hadrons does however have a charge that is a multiple of the electron charge.
Why is electric charge quantized? That is, why do all charges come in multiples of $e$? Paul Dirac attempted to find a solution to this by showing that the existence of magnetic monopoles would require that electric charges come in discrete multiples. In very simple terms, the basic argument is that if there are magnetically charged particles (magnetic monopoles) they too must have well-defined quantum states, and that this requirement places a constraint on electrical fluxes. That constraint leads to the requirement that electrical charge be quantized. For a derivation, see here: