Understanding Superposition in RC Circuits with Kirchoff's Law

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SUMMARY

This discussion focuses on the application of Kirchhoff's Law in analyzing RC circuits with time-varying electromotive force (emf) represented by U(t) = a0 + Ʃaicos(ωt). It establishes that while Kirchhoff's Law is linear and can be applied to each term independently, there are physical implications when considering the steady-state behavior of capacitors. Specifically, after an infinite amount of time, the constant component a0 results in no current due to the capacitor blocking it, yet raises questions about the additional charge on the capacitor and its effects on circuit behavior. The discussion emphasizes the need to reconcile these theoretical observations with practical circuit analysis.

PREREQUISITES
  • Understanding of Kirchhoff's Laws in electrical circuits
  • Basic knowledge of RC circuit behavior and components
  • Familiarity with time-varying electromotive forces (emf)
  • Concept of superposition in linear systems
NEXT STEPS
  • Study the implications of Kirchhoff's Law in non-linear circuits
  • Explore the concept of superposition in electrical engineering
  • Learn about the transient and steady-state analysis of RC circuits
  • Investigate the effects of initial conditions on capacitor charging in RC circuits
USEFUL FOR

Electrical engineers, physics students, and anyone interested in circuit analysis, particularly those studying the behavior of RC circuits under varying electromotive forces.

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When you work with an emf of the form:

U(t) = a0 + Ʃaicos([itex]\omega[/itex]t)
it desperately cries for using Kirchoffs law for each term in the sum independently. I guess you can do so since Kirchoffs law is linear but then other the hand I get something weird physically when doing so.
In every exercise I am told that the current has been going on forever. Applying Kirchoffs law for the current due to a0 after an infinite amount of time then shows that there is no current due to this. Which I guess makes sense because for a circuit where the only emf is generated by the constant because then after an infinite amount of there is no current because the capacitor is blocking everything because of the charge on it. But on the other hand when you then superposition this situation with a lot of other emfs that are oscillating something is weird physically- because shouldn't the "extra" charge on the capacitor arising from the constant part of the emf not give rise to a different physical situation? I mean even though there is no current due to it has produced some extra charge on the capacitor which generates a potential drop for every electron going towards the - pole. Shouldn't this somehow be accounted for?
 
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Please show the circuit you are referring to.
 
it's a simple RC-circuit
 

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