I saw a video on magnetic monopoles. In it the presenter spoke about quantised charges and said there is no reason we can’t have fractional charges. Can I ask why did he make that statement?

Question

Given electrons and protons are what we consider fundamental particles and both have a charge of -1 or 1 does it not just make sense we can only have charges in integer multiples of that?

I understand quarks have a 1/3 charge but for the purpose of this discussion I think we can ignore that. We can also ignore magnetic monopoles really that was just a lead in to my question.

(copied from my response to mcgato)

In: Physics

Answer 1

First off all, fractional charges are still quantised charges. It just means fractional with respect to the electron charge. Quarks have a fractional charge of 1/3 or 2/3 (ignoring minus signs). So if you define the quantum of charge as 1/3e, where e is the electron charge, then there only exist particles with integer multiples of the quantum charge in nature (in terms of fundamental particles at least).

Now, the reason you’ll never physically measure a fractional charge is because of something called ‘quark confinement’. It basically means that quarks can’t freely exist on their own – only together with other quarks – always in such a way that the total charge is an integer multiple of the electron charge.