Excellent example. Diagram 1 is all you need. L directly passes DC current, and low A/C frequencies also pass depending on the size of the inductor. In a sim

Excellent example. Diagram 1 is all you need. L directly passes DC current, and low A/C frequencies also pass depending on the size of the inductor. In a simplified way the component alone acts as a low-pass filter. C doesn't pass DC, but with A/C beyond a certain frequency in a simplified way it has no problem "broadcasting" a signal from one plate to the other within the capacitor, thereby delivering that portion of the Alternating Current to flow across the dielectric to the extent the size of the capacitor allows. Even audio signals that are nowhere near radio frequency will "broadcast" faithfully across such short physical distances which are intended for the exact purpose. C acting then as a high-pass component. For any given frequency, if L is large enough to completely filter that frequency from passing, then the only current conducted is what is needed to initially charge C to a steady state. In the equation both L & C are equal weighted and behave identically, theoretically. If L is infinite, as long as C is nonzero, no A/C current flows regardless of frequency. But if C is infinite, current flows forever without ever fully charging the capacitor, so that's like a black hole. An ideal inductor has no internal resistance and presents no stray capacitance. An ideal capacitor has no stray inductance and zero Equivalent Series Resistance. Even though ideal components like that don't actually exist, that doesn't have any bearing on the theory used to explain the behavior. But in the real world each component has a functional value. Nothing is infinite (but there are "zero ohm" resistors). The theory's still OK, you really need to use realistic component values and frequencies for everything to make sense. Ideally, it's probably better not to confuse infinite with ideal.