Need L and C to be in series in order to have a RLC series circuit?

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Discussion Overview

The discussion centers around the configuration of components in an RLC circuit, specifically whether an inductor (L) and capacitor (C) must be in series to classify the circuit as a series RLC circuit, and the implications of the placement of a resistor (R) in relation to L and C.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that for a circuit to be classified as a series RLC circuit, all three components (R, L, and C) must be in series.
  • Others propose that while R should be in series with L and C, a resistor in parallel with the LC pair could be transformed into a series configuration through network transformation theorems.
  • One participant explains that interchanging R and L does not affect the circuit's behavior, but interchanging L and C changes the circuit type from low-pass to high-pass, indicating the arrangement of L and C is significant.
  • Another participant questions the context of the original question, emphasizing the definition of a series RLC circuit.
  • There is a suggestion that arbitrary configurations of R, L, and C may not fit neatly into the definitions of series or parallel RLC circuits.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the necessity of having R, L, and C in series for the circuit to be classified as a series RLC circuit. Multiple competing views regarding the arrangement and classification of the components remain unresolved.

Contextual Notes

There are limitations in the discussion regarding the definitions of series and parallel configurations, as well as the implications of component arrangement on circuit behavior, which are not fully explored.

Swapnil
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Do you only need L and C to be in series in order to have a RLC series circuit? (So where you put R doesn't matter right?).
 
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Strictly speaking no, the R should be in series with L and C too. Then again, an R which is in parallel to the LC pair could be converted (with network transformation theorems) to being in series to it.

So I guess there is really no straight answer to this question.
 
Swapnil said:
Do you only need L and C to be in series in order to have a RLC series circuit? (So where you put R doesn't matter right?).

RLC series circuit implies that RL are in series & C is shunted to the ground, that again implies that we have a low-pass circuit of second order (capacitor provides an escape route for high frequency). Now interchanging R and L will have no affect on the circuit, since they are in series (circuit will have same fc etc.) But if you interchange L & C you will end up with a high-pass circuit, since the capacitor will exhibit high Xc for low frequencies and low Xc for high frequencies. So it does matter in how you arrange the L&C, but it doesn't matter in how you arrange the R&C.

P.S You can prove this by writing a transfer function for the both circuits (swapped R) using laplace and you'll end up the similar functions.
 
Swapnil said:
Do you only need L and C to be in series in order to have a RLC series circuit? (So where you put R doesn't matter right?).

A series RLC circuit has all 3 elements in series. That's why it's called a "series RLC circuit" after all. Is there a context to this question?
 
berkeman said:
A series RLC circuit has all 3 elements in series. That's why it's called a "series RLC circuit" after all. Is there a context to this question?
Its just that you have these equations for a series and a parallel RLC circuit so I was wondering if you have circuit which has any arbitrary configuration of a resistor, a capacitor, and an inductor, would you always be able to call it either a series or parallel RLC circuit?
 

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