Okay - maybe not the most advanced question, but one I have not seen a satisfactory answer to.
DC current is easy to understand. The current and electronics flow unidirectional, and you can understand how by connecting a circuit, a flow goes from the source to the recipient end of the circuit, and by passing through some form of resistance (say a filament on a light bulb), generates heat.
As for AC current, I get it. Once the circuit is on, the electrons pass back & forth. I understand that concept. What I do not understand is how the circuit ever gets created in the first place. Bear with me:
If ultimately, the current is flowing back and forth, how does it ever move forward from the source to the end-point of the circuit in the first place? I have heard of a golf-ball in a pipe analogy to explain how an AC circuit n works....but what no one explains is how the current flows when first putting all the golf balls into the pipe in the first place (as an analogy).
Are the electrons already there (i.e - a component of the material over which current flows)...but even then, if the current oscillates back-and-forth, how does it ever move forward to create a circuit?
The only analogy I thought of that might explain this is that the current itself (the flow of electricity moves unidirectional), but the electrons oscillate. So an analogy in that case might be that the current is a river, while the electrons are fish swimming back and forth?)
Apologies in advance for such a naive question, but this I have never been able to get a sufficient explanation for this.