But can electromagnetism at all emerge if the quantum mechanics dont exist to emerge things like magnetism and some of the behavior of electrons?
Well yeah, sure. Earlier you said something like “electromagentism is caused by quantum phenomena,” but you can say that about almost every object and behavior in the universe! We don’t have a theory of everything but the standard model and quantum field theory explain a lot.
WolfLink@sh.itjust.works 6 hours ago
Short answer: yes.
Technically the world can’t exist without all of its physics. But that’s kinda backwards from how you study it. Quantum mechanics isn’t “more correct” than classical mechanics, it’s more that it’s “more detailed”.
If you want to model an electromagnet, an electronic circuit, light (in most macroscopic situations), how permanent magnets interact, electrostatic situations like how static electricity makes your hair stand up, lightning, the magnetic fields of celestial bodies like the Earth and Sun (they are big electromagnets), etc. you will use “classical” electromagnetism (meaning Newton’s mechanics, possibly with Einstein’s modifications, and Maxwell’s equations).
If you want to model material science situations, like determining what material to make a diode or transistor out of, or if a given material can become a permanent magnet, you will likely need quantum mechanics to help model the interactions of electrons on the atomic scale. The section on Wikipedia you were looking at is about this kind of material science. You do this by combining the same “classical electromagnetic” equations with Schrödinger’s equations for quantum mechanics.