Voltage across R, L and C vs AC Voltage source in RLC Series Circuit

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Discussion Overview

The discussion revolves around the behavior of voltage across resistive (R), inductive (L), and capacitive (C) components in a series RLC circuit when subjected to an AC voltage source, particularly at resonance. Participants explore intuitive explanations and analogies for the phenomenon where the voltages across these components can exceed the source voltage, contrasting this with DC circuits.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes the counter-intuitive nature of voltage across R, L, and C at resonance being larger than the source voltage, relating it to a vector analogy.
  • Another participant offers an analogy involving a swinging weight to illustrate how small, repetitive forces can lead to large displacements, suggesting a parallel to resonant circuits.
  • A participant challenges the terminology used in describing voltage across inductance, asserting that it should be referred to as EMF and citing Faraday's Law to support their claim.
  • A repeated assertion emphasizes the need for clarity in terminology regarding voltage and EMF in time-varying magnetic fields.
  • A participant shares a link to a lecture on electromagnetic field theory, suggesting it may provide additional context or help.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and conceptual understanding of voltage in inductive components, with some advocating for a more precise language while others focus on intuitive explanations. The discussion remains unresolved regarding the best way to describe these phenomena.

Contextual Notes

There are unresolved assumptions regarding the definitions of voltage and EMF in the context of inductance, as well as the implications of resonance in RLC circuits. The discussion does not clarify the mathematical underpinnings of these claims.

Zahid Iftikhar
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One property of series resonance circuit is that at resonance, the voltage across circuit elements R,L and C may be larger than the source voltage. I can relate it to vector analogy where component vectors may have larger values than the resultant and the phenomenon is counter-intuitive. This does not happen in DC circuits where sum of voltage across circuit components is always equal to the source voltage. Any useful intuitive explanation of this effect please?
Characteristics of RLC Series Circuit.PNG
 
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A useful analogy for resonant excitation is to think about a swinging weight on the end of a rope, and you pushing it at the extreme of each swing with a small force and displacement with your fingertip.

As long as the losses are low for the swinging weight, it takes very small repetitive/resonant forces and small pushes from your fingertip to make it build up a large swing displacement -- much larger than the small periodic push amplitude of your fingertip...
 
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It's simply sloppy! Don't use such sloppy books! There's no voltage across an inductance, it's an EMF. In time-varying magnetic fields, there's no potential for the elctric field due to Faraday's Law, which is one of the fundamental Maxwell equations,
$$\vec{\nabla} \times \vec{E}=-\frac{1}{c} \partial_t \vec{B}.$$
 
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vanhees71 said:
It's simply sloppy! Don't use such sloppy books! There's no voltage across an inductance, it's an EMF. In time-varying magnetic fields, there's no potential for the elctric field due to Faraday's Law, which is one of the fundamental Maxwell equations,
$$\vec{\nabla} \times \vec{E}=-\frac{1}{c} \partial_t \vec{B}.$$
Thanks. I need more help on this please.
 

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