RLC Circuits - Q Factor and Amplitude

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Homework Help Overview

The discussion revolves around the behavior of two RLC circuits with different Q-factors as the driving frequency is varied away from resonance. The original poster is trying to understand how the amplitude response differs between a high Q-factor circuit and a low Q-factor circuit.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to interpret the meaning of changing the driving frequency away from resonance and relates Q-factor to resistance and inductance. Some participants suggest focusing on the qualitative aspects of Q-factor and its relationship to resonance behavior rather than quantitative calculations.

Discussion Status

The discussion is ongoing, with participants exploring the implications of Q-factor on amplitude response. Some guidance has been offered regarding the qualitative nature of the question, emphasizing understanding the physical representation of Q in relation to resonance.

Contextual Notes

Participants note the absence of specific values in the problem, which influences the approach to the discussion, leaning towards qualitative analysis rather than quantitative solutions.

wjdgone

Homework Statement


Imagine you have two RLC circuits you are trying to scan for resonances. They have identical resonant frequencies, but circuit 1 has a very high Q-factor
(Q1 >> 1), and circuit 2 has a very low Q-factor (Q2 < 1). Let's assume you are already
on resonance and looking at V(out) on the oscilloscope, and you change the frequency in either direction for both circuits. How will the amplitude response differ between circuits 1
and 2 as you move the driving frequency away from resonance?

Homework Equations



Q=R/(2*pi*f*L) - not sure if I need this in the first place

The Attempt at a Solution


I don't think I understand what the problem means by "as you move the driving frequency away from resonance." My best blind stab in the dark for this problem is that Q1 means that R>2*pi*f*L and Q2 means that R<2*pi*f*L, and I can relate the inductance to the change in amplitude such that if inductance decreases, amplitude increases? (I'm also not sure how to relate inductance to amplitude.)
 
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wjdgone said:
not sure if I need this in the first place
You can use it if you know the definition of ##Q## and understand what they mean with ##\Delta \omega ## :rolleyes:
 
BvU said:
You can use it if you know the definition of ##Q## and understand what they mean with ##\Delta \omega ## :rolleyes:
I still don't understand how I can determine what amplitude does.
 
Since you are not given any values at all, I'd take this as a qualitative question rather than quantitative.
What you need to understand is what Q represents and how it relates to resonance behviour.
I expect many PF readers will be best able to get this from the formulae, but I find the simple notion of what Q represents physically, shown vividly in graphs of amplitude vs frequency, is the easiest way to understand what will happen in the situation described - and no calculations needed!
 

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