I'm curious to understand the properties behind direct current (DC) and alternating current (AC) which started when reading the definition and several articles online that, "AC periodically reverses direction and changes its magnitude continuously".
My understanding is that: current is the amount of charge per time, voltage is the potential of the electric field, and energy is an electromagnetic wave. So if the potential of an electric field is propagated by an electromagnetic wave, which is like \$E = E_0e^{iwt}\$ and therefore has some (maybe not uniform?) amplitude and phase which is related to the electric potential as the voltage, then shouldn't all currents also follow an oscillatory behaviour like \$i(t) = I_mcos(\omega t+\phi_i)\$ ?
Then I discovered the rectifier, which somehow filters out all of the phases which have the opposite sign:
Although, now this looks a little more like a pulsating "current"? Do more filters need to be added in order to make a direct current? I can sort of understand this if the system goes into a steady-state or something like it builds up a standing wave.
How can we get the direct current and alternating current to directly arise? Would it be dependent on the materials like metals / dielectrics? It makes sense to me that a galvanic cell gives rise to a direct current since the chemical potentials make it extremely unlikely for ions to flow in the opposite ways but this feels a little different to me.
Finally, does "alternating current changing directions" just mean the phase changes 180\$^o\$ in a given length of time? I'm not sure how to imagine this physically.
Thank you very much !
Links:
(1) graphs
(2) rectifier