Video Transcript
How many quarks are there in a proton?
Now to answer this question, we first need to recall that both protons and neutrons, the two kinds of particle found in the nuclei of atoms, are made up of even smaller particles. These smaller particles are known as quarks and specifically protons and neutrons are made up of up quarks and down quarks. Now, if we think about the relative charges on all of these particles, then we can recall that a proton has a relative charge of positive one. in other words, it’s a positively charged particle. And the neutron has a relative charge of zero. It’s a neutral particle. Additionally, an up quark has a relative charge of positive two-thirds and a down quark has a relative charge of negative one-third.
So now, let’s realise that if we’re to combine up and down quarks together in a specific way, such that the overall charge has to be positive one because we’re trying to make a proton. Then we can realise that if we combine two up quarks with one down quark, then the total charge ends up being positive two-thirds from one of the of the up quarks plus another two-thirds from the second up quark minus one-third from the down quark. And altogether this adds to give us an overall charge of positive one, just like the charge on a proton. And so at this point we see that there are three quarks in a proton, two up quarks and one down quark. And, hence, we found the answer to our question.
