I'm going back to fundamentals in electronics, and I end up with questions that I can't answer satisfactorily.

The object of my turmoil is the

**parallel LC circuit**, and more especially what happens when it is connected to an AC voltage source that delivers a sine signal at the resonance frequency of the LC circuit.

I'm trying to "get what's happening" without using Kirchhoff's laws, because I want to seize the physical phenomenon instead of proving it mathematically. Showing algebraically that the global impedance of the parallel LC circuit is maximum at resonance frequency does not satisfy me because I want visualize what the charges do in the circuit.

__My questions comes from this thinking of mine:__

Imagine you connect that AC source to the parallel LC circuit,

**without having charged the C nor the L before, and neglecting resistive effects**. And imagine that the AC source delivers a sine signal

**at the resonance frequency of the LC circuit**.

Now I will describe what I think happens, please correct me if I'm wrong.

During the first quarter cycle of the sine signal,

**starting with a**(

__positive__voltage**STEP 1**):

- The C (capacitor) gets charged, the current through it going from max value to zero, and the voltage at its ports from zero to max value (following the input AC voltage).

- As for the L (self), the voltage at its ports follows also the input AC voltage, and at the end of the quarter cycle (max positive voltage), the current through it is just about to be positive (the current drags 90 degrees with respect to the voltage at the L ports, as its reactance shows).

Then (

**STEP 2**), the AC voltage starts to decrease (starting the second quarter cycle, just after the max voltage). Therefore, the positive charges accumulated on the positive plate of the C will start to leave the plate as stated by q = Cu (I won't dive into the specifics of drift velocity vs wave velocity, but think in terms of travelling charges instead).

My understanding is as follows:

1) The positive charges leaving the positive plate of the C will go through the L, and the "90 degrees delayed" positive current through the L will correspond to that flow of charges from the C to the L (because at resonance, the

**modulus**of the C-reactance equals the

**modulus**of the L-reactance).

2) As a result, the C is not "asking for" current anymore, and all the current is L is "asking for" comes from the C.

3) As a consequence of 2., the current from the AC source will now be zero, meaning that the impedance of the parallel AC circuit can be considered infinite (open circuit). The voltage between the two ports of the LC circuit will continue oscillating (we neglect the resistive effects), with no current ever delivered by the AC source anymore.

So my questions are:

1. Is what I describe correct ?

2. About point 1), it is correct to assume that it's the electromotive force induced by the L that make the positive charges from the C travel through the L instead of going back to the positive port of the AC source ?

I apologize for not bringing any plots to support my question, but I guess you are familiar enough with the topics to get my point.

With my best regards,

Takotak