In an RLC circuit the Mathematics says that some voltage is stored in the LC portion of the circuit, and the rest goes to the resistors, unless the source is oscillating at the resonance frequency.

I get the Math, but I just don't get it physically, why is the resonance frequency is so special? I guess it has something to do with the Energy exchange between the inductor and capacitor, but then how does this take place in the beginning of the operation when both the inductor and capacitor are empty of Energy.

Thanks, looking forward to reading from you.

  • 1
    $\begingroup$ In the comment below, you are asking "ignore the transient state" and yet in the question you say "how does it take place in the beginning". The time from "beginning" to "steady state" is the transient state, and you either ignore, it, or you don't. That makes it unclear what you are asking. $\endgroup$ – Floris Jan 6 '18 at 19:00
  • $\begingroup$ He said that they're different states, so I urged him just to concentrate on the steady state as a beginning. $\endgroup$ – Raafat Abualazm Jan 6 '18 at 19:44
  • $\begingroup$ "I get the Math" - you've considered then a source of the form $v(t) = V_0\,e^{i\omega_0t}u(t)$ where $u(t)$ is the Heaviside step function? $\endgroup$ – Alfred Centauri Jan 7 '18 at 1:11
  • $\begingroup$ After tking the inverse Laplace, so yes. $\endgroup$ – Raafat Abualazm Jan 7 '18 at 13:06
  • $\begingroup$ I want o understand it physically. What actually happens. $\endgroup$ – Raafat Abualazm Jan 7 '18 at 13:06

The math you probably refer to (complex impedances), is relevant for the final steady state. For transient behavior, when circuit is just connected, you need to apply time domain math which takes into account initial conditions at the capacitor and inductor.

  • $\begingroup$ Let's ignore the transient state then. $\endgroup$ – Raafat Abualazm Jan 6 '18 at 18:42
  • $\begingroup$ How can the oscillating voltage source be blind to the existence of capacitors or inductors at the resonating frequency. Physically. $\endgroup$ – Raafat Abualazm Jan 6 '18 at 18:43
  • $\begingroup$ The voltage source doesn't "see" anything. Its role is creating an oscillating voltage with a specified amplitude. Current changes in accordance with the circuit components. A capacitor can "add" an out-of-phase current. So does an inductor. At specific circumstances, the total currents from the reactive components cancel one another. $\endgroup$ – npojo Jan 6 '18 at 19:22
  • $\begingroup$ Can you clarify please? I'm not sure I understand $\endgroup$ – Raafat Abualazm Jan 6 '18 at 19:45

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