Critically damped current in this network

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Discussion Overview

The discussion revolves around determining the damping condition of the current in an electrical network involving resistors, inductors, and capacitors. Participants explore the criteria for under-damped, critically damped, undamped, and over-damped states, referencing relevant equations and concepts from circuit theory.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant states that the professor indicated the system is "b) critically damped" based on given component values.
  • Another participant provides the condition for critical damping as \(\alpha^{2}-4\omega^{2}_{o}=0\) and suggests that using the formula \(R=\sqrt{4L/C}\) with the provided values will confirm critical damping.
  • A participant acknowledges a mistake in their calculations related to the roots necessary for determining critical damping.
  • One participant questions the conditions under which a circuit would be considered undamped, noting their understanding of other damping states.
  • Another participant clarifies that the presence of a resistor implies energy loss, leading to damping, while an LC circuit without a resistor would oscillate without damping.

Areas of Agreement / Disagreement

Participants express differing views on the conditions for undamped circuits, with some agreeing that resistors cause damping while others seek clarification on undamped scenarios. The discussion does not reach a consensus on the exact conditions for undamped circuits.

Contextual Notes

Participants reference specific values for resistance, inductance, and capacitance, but the discussion includes unresolved calculations and assumptions regarding the relationships between these components and their impact on damping.

Who May Find This Useful

This discussion may be useful for students studying circuit theory, particularly those interested in the behavior of RLC circuits and the concepts of damping in electrical systems.

EEZeroo
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Homework Statement


I'm supposed to find whether the current in the following network is

a) under-damped
b) critically damped
c) undamped
c) over-damped

69a41e90b3645d9e7114cb87b7e00ab2.png


Homework Equations


According to Kirchoff's laws
c14ee8367ddccabff780a7275dd9f322.png


The Attempt at a Solution



The answer given by my professor for this question is supposed to be "b) critically damped" so I just converted the given values into SI values
R = 1kilo-ohm = 1000 ohm
L = 10mH = 0,01H
C = 40nF = 4 * 10^(-8)

and then I tried relating them to

3e2c036273361ac3e5a5bc528b59cc44.png


But I do not find two real roots that are equal for it to be critically damped.

What did I do wrong?
 
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Critical damping will occur when [itex]\alpha[/itex][itex]^{2}[/itex]-4[itex]\omega^{2}_{o}[/itex]=0. Another way to write it is: R=sqrt(4*L/C). If you plug in your values for R, L and C, you'll find that it is indeed critically damped.
 
Thank you. I see that my silly mistake was that I substracted the 10 instead of leaving it homogenous.

Though, when exactly is a circuit undamped? I know when it's critically, overdamped or underdamped but when would it be undamped?
 
If there's a resistor, there will always be energy lost, hence the damping.
An LC circuit (no resistor) will oscillate without damping.
 

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