Electric current can be studied using classical electromagnetism. In that case, the explanation is that there is a net flow of free electrons through a wire, say. Looking more close on the situation, what happens is that there is a difference on the energy level of some atoms and electrons can flow from one to another. -- Excuse me if I'm wrong at this point. Anyways, my question is, Is it appropriate to explain the phenomenon of electric current using quantum mechanics? Maybe, the electrons get excited and jump off from one energy level to another one?