That something is negatively charged by an excess of electrons or positively by an excess of protons. But what causes a negative or positive charge in a single particle?
Answer
What exactly is charge? This is a very basic question. Here’s an attempt at an answer that will hopefully shed some light, or at least shed some light on the question.
Matter is made up of elementary particles, and those particles have a number of properties. For example, a particle can have mass, spin, … and also a particle can have charge. Charge is therefore not an object in itself, it is a property of an object. When you encounter a charge, it is always linked to a certain particle. The charge of the particle determines how the particle reacts to the electromagnetic field, and also contributes to it through its charge. Compare it to color in our everyday world: a car can be white, a wall can be white, but you will never come across a “white”. If you want to use/see the term, it is always as a property of an object.
The charge can be positive or negative, and a particle can also be neutrally charged. Such is the case with a neutron. But if you look at that neutron in detail, it turns out to be made up of three even smaller particles, each of which has the property of “charge”. A neutron contains two down quarks (each with charge -1/3) and one up quark (with charge 2/3). Whether quarks are made up of even smaller particles is not known. The same goes for electrons. An electron has a charge of -1, but even there we do not know whether the electron is composed of even smaller objects. For now, quarks and electrons are considered point-shaped fundamental particles with no internal structure. And yet, and yet they have properties that make an up quark different from an electron.
I realize that this answer to your question may not satisfy you 100 percent. Actually, I move the problem a bit, because now you can rightly ask, what is such a property of an elementary particle? Well, those properties are there, and they determine the nature of the particle, in other words, how it reacts to the fundamental force fields.
It might be useful to take a look at these, albeit in English, websites:
http://amasci.com/elect/charge1.html
http://www.dctech.com/physics/features/0801.php
Answered by
prof.dr. Paul Hellings
Department of Mathematics, Fac. IIW, KU Leuven
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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