What is charge, really?

We’ve all heard about this particular term, right? Back in high school, back when the world seemed so simple and straightforward.

But after venturing off into the knowledgeable reaches of the internet and the collection of scientific textbooks at my disposal, I only ended up with a vague answer to understanding charge.

Photo by Bamdad Norouzian on Unsplash

Yes, we all know that electric charge, be it positive (+) or negative (-), is a fundamental quantity of matter that is the culprit for determining interactions via the electromagnetic force — one of the four forces of nature. We also should be familiar with quantization of charge, meaning that it always comes in discrete packets rather than some continuous spectrum.

But… the question still looms:

What causes charge?

As of now, I am enrolled in a Subatomic Physics course in university. And my subconsciously curious mind couldn’t help but wonder what is the reason behind charge.

The spin of a particle — be it lepton, quark or boson — is responsible for providing its charge, then what might be happening around a particle for which it is either attracting or repelling other neighboring particles?

Well, the spin itself does NOT make the particles attract or repel anything! However, it aids in generating magnetic moments (spinning forces). When particles such as electrons interact with one another, those with parallel spins can experience a magnetic attraction, while those with antiparallel spins can experience a magnetic repulsion. This is already evident in the behavior of electrons in magnetic materials.

Another reason for particles to repel each other is an application of the Pauli Exclusion Principle.

Particles with half-integer spin (e.g. electrons) obey Fermi-Dirac statistics and are subject to the Pauli Exclusion Principle. This principle states that no two fermions (e.g. protons, neutrons) can occupy the same quantum state simultaneously. This leads to the “repulsion” of particles with the same quantum state because they cannot occupy the same space with the same quantum numbers (e.g., same energy level, same orbital).

Photo by Hal Gatewood on Unsplash

However, the electromagnetic charge (that we discussed above) isn’t the only kind of charge known to mankind; there’s another kind of charge found within nucleons, dubbed the “color charge” — which is a topic for another day. 😄