RLC Parallel Circuit: Solving for Current & Energy

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Discussion Overview

The discussion revolves around solving for current and energy in a parallel RLC circuit, focusing on the application of circuit laws and equations. Participants explore how to approach the problem, including the use of formulas and concepts related to reactance and impedance.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks guidance on calculating the current through each component of the RLC circuit using formulas for resistors, inductors, and capacitors.
  • Another participant suggests using Kirchhoff's laws and notes that the current is already provided for the inductor at t=0, implying that this value should be used for further calculations.
  • A later reply emphasizes the need to apply knowledge of AC equivalent circuits, reactances, and impedances to derive a solution rather than relying on existing equations.
  • One participant expresses confusion regarding the instructions and seeks clarification on how to find the current going into the inductor.
  • Another participant acknowledges the complexity of the topic and expresses a willingness to attempt the problem after some initial confusion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to solve the problem, with differing interpretations of the instructions and the application of circuit laws. Some participants emphasize the need to derive solutions based on understanding rather than existing formulas.

Contextual Notes

There is uncertainty regarding the specific equations applicable to the circuit in question, as well as the assumptions underlying the use of Kirchhoff's laws and the calculation of energy stored in the components.

Who May Find This Useful

Students studying electrical engineering or physics, particularly those working on circuit analysis and energy calculations in RLC circuits.

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Homework Statement



See image

Homework Equations



.5Li2
.5Cv2

The Attempt at a Solution



How do I calculate the current for a circuit of this type? I am unable to find any examples in our text. Can I use the following formulas to solve for the current flowing through each component:

I(r) = V/R
I(L) = V/X(L)
I(C) = V/X(C)

Would it be possible to find the energy stored in each component at t = .4 s?

Or would it be okay to use the energy equations for the L and C, accordingly.
In this case, .5(100^2)10*10^-6 = 50mJ
 

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How do I calculate the current for a circuit of this type?
You are given the current.

You can use kirkoffs laws.
You also have some notes about finding equivalent impedences and/or reactances and so on.
You are expected to use that information to solve problems you have not seen before.
 
Simon Bridge said:
You are given the current.

You can use kirkoffs laws.
You also have some notes about finding equivalent impedences and/or reactances and so on.
You are expected to use that information to solve problems you have not seen before.

huh? I'm not sure what you mean by your last two sentences...

I need to find the current going into the inductor, I wasn't sure if I was supposed to use the I(L) in order to find tat.
 
The problem statement you provided in the attachment does not tell you to find the current ... you are given the current for the inductor at t=0.
To find the current at another time, you will need to use this value.

huh? I'm not sure what you mean by your last two sentences...
... let me clarify:

When you said:
I am unable to find any examples in our text.
- this means that this is a problem you have not seen before. You are expected to be able to use knowledge you learn in your coursework to solve problems you have not seen before.

You asked about how to find currents and stored energy for a circuit like that.
How do I calculate the current for a circuit of this type?...
Would it be possible to find the energy stored in each component...
To do that, you have to use your understanding of AC equivalent circuits, reactances, and impedences.
You should have some notes in your coursework, and in the textbook, about these things already.

I want to get you off trying to find an existing equation and on to using your understanding of physics.
Chances are you don't have an equation to cover exactly this circuit - so you'll have to derive one.
 
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I will give it a try and take a look at it. My mind turns into spaghetti after looking at this stuff too long! My apologies for the confusion.
 

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