I can understand why in DC analysis we remove capacitors since the caps do not pass DC in steady state. This is easy to conclude because in reality the DC component of a current do not pass through a capacitor.
But in AC analysis there is a concept called "AC ground", which means we basically ground the Vcc to the real ground. I'm having hard time to understand this. Because in real the AC component of the current does not flow upwards to the Vcc(? not sure). How come then the Vcc is grounded as if the AC component of the current will flow into the Vcc?
Let's look at the below example transformation for AC analysis:
Above on the left, if the circuit is in linear mode and if a sinusoidal small vbe applied to its base, there will be an ic collector current which is composed of a DC offset Ic0 plus an AC component call it ic. The total collector current will look like this:
Considering the above total collector current ic, what can we say about the current direction? Does AC part of the current flow into the Vcc back and forth or not(in reality)? Because in AC analysis we short the Vcc ground as if the current flows into Vcc back and forth. I hope I could articulate where I'm confused.