We all know that protons are positively charged, and electrons are negatively charged. It is also known that electrons are lighter than protons, and they both attract each other. Both have the same magnitude of charge but due to some historical background, they have been + and - (the sign convention). But my question is that what actually are they, we say that they are fundamental units of matter, but now it is known that they are made of quarks (except electrons) and all that stuff. Whatever they may be, they are charges, but what charges actually are? If we forget what are protons and electrons, then how will we describe them? I know that the answer would surely be in QM, but I don't know much about it. So, please it is my request to tell the basic meaning of the terms used in the equations which would be there in your answer.
2 Answers
If only we knew what charge is... Actually Quantum Field Theory does not answer that. Charge tells you how different particle fields interact, but it does not arise from the theory in a natural way. Actually, Quantum Electrodynamics is so accurate because it was built upon Classical Electrodynamics, but most of its problems stayed within the new theory (for example self energy of the electron). In that sense, the theory does not give new insights.
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Charge is a property of matter, so one can only talk of the property and what it does, like equally charged matter repels each other, different charged matter attract each other. Same thing for "mass"! It is a property of everything around us. So charge is always together with matter. The only thing known: there is a smallest amount of charge which is that of an electron or its antiparticle the positron. All material is made of atoms which consist of positive nuclei and negative electrons, their charges neutralize each other normally. So your question: what is charge has not a real answer, we can only describe what the property of being charged does
