Understanding Superposition in RC Circuits with Kirchoff's Law

In summary, when working with an emf of the form U(t) = a0 + Ʃaicos(\omegat), it is necessary to use Kirchoff's law for each term in the sum independently. However, this can lead to strange physical results, as seen in the case of an infinite current being applied for the a0 term. This makes sense for a circuit with only a constant emf, as the capacitor blocks all current after an infinite amount of time. However, when superimposing this with other oscillating emfs, the presence of extra charge on the capacitor raises questions about the physical situation. This is especially evident in a simple RC-circuit.
  • #1
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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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  • #2
Please show the circuit you are referring to.
 
  • #3
it's a simple RC-circuit
 

FAQ: Understanding Superposition in RC Circuits with Kirchoff's Law

What is current superposition?

Current superposition is the principle that states that the total current in a circuit is equal to the algebraic sum of the individual currents caused by each voltage source in the circuit.

How does current superposition apply to circuits?

In circuits, current superposition allows us to analyze the behavior of a circuit with multiple voltage sources by considering the effects of each source separately and then combining them to find the total current.

What is the advantage of using current superposition in circuit analysis?

The advantage of using current superposition is that it simplifies the analysis of complex circuits by breaking it down into smaller, more manageable parts.

Does current superposition work for both DC and AC circuits?

Yes, current superposition can be applied to both DC (direct current) and AC (alternating current) circuits. However, it is important to note that the principle only applies to linear circuits, where the current is directly proportional to the voltage.

Are there any limitations to using current superposition in circuit analysis?

Yes, there are limitations to using current superposition. It can only be applied to linear circuits, where the current and voltage are directly proportional. It also assumes that there is no interaction between the individual voltage sources, which may not always be the case in more complex circuits.

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