I need a 2nd opinion on a circuit analysis answer

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Discussion Overview

The discussion revolves around the analysis of a circuit using superposition to determine the current through an inductor (I_L). Participants explore the implications of treating current sources as either AC or DC based on the information provided in the problem statement.

Discussion Character

  • Debate/contested
  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant calculates I_L for a current source treated as DC, yielding a specific value, but questions whether this treatment is appropriate given the context of the circuit.
  • Another participant suggests that the problem should explicitly define whether the 20mA current source is AC or DC, indicating a lack of clarity in the question.
  • A participant expresses frustration over being marked wrong for their interpretation of the source type, suggesting a potential miscommunication with the professor.
  • Some participants propose that the presence of a "+" sign next to the current source implies it is a DC source, while others challenge this by noting that a similar notation appears next to an AC dependent voltage source.
  • One participant suggests offering both solutions (AC and DC) if clarification is not available during a test, indicating a strategy to address ambiguity in the question.
  • There is ongoing uncertainty about the meaning of the "+" sign next to the current source, with participants questioning its relevance and implications for the source type.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the current source should be treated as AC or DC, with multiple competing views remaining regarding the interpretation of the circuit elements.

Contextual Notes

The discussion highlights limitations in the problem statement, particularly the lack of explicit definitions for the source types and the potential for misinterpretation based on the notation used.

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Homework Statement


Use superposition to find [tex]I_L[/tex]

superposition.jpg


Homework Equations


-The overall current is the sum of the currents supplied by each source individually


The Attempt at a Solution



for source B only (current source is open):

---ohm's law: [tex]\frac{100V}{15k + j25k} = 3.43mA( -59.04 degrees)[/tex]

Here is where I'm having to defend my answer:

for souce A only (voltage source shorted):

---since there is no phase shift labeled, it should be assumed that the current source can be treated as a DC source, treating the inductor as a short, making [tex]I_L[/tex] -20mA

Is this wrong? Should I treat a current source as AC if it has other AC sources involved in the circuit? If this is so I'd just do a current divider to get [tex]I_L[/tex]
 
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I believe the question would have to be more explicit in defining whether the 20mA is an ac or dc source.
 
Well no extra information was given than what's shown, yet I got it marked wrong for treating it one way over the other...

Am I going to have to call out my professor again? I'm losing all my brownie points because of his dud test questions
 
I would imagine the "+" by the current source tells you it's a dc source.
 
Well actually he graded it as it being an AC source.
 
If you are answering the question as part of a test and if the professor is not available to clarify, then I guess you could always offer both solutions, one for each case.

Failing that, then I suppose at the last resort you should treat it as ac since, as you said, there are other ac sources in the circuit.
 
Gokul43201 said:
I would imagine the "+" by the current source tells you it's a dc source.

Hmm... but a "+" sign also appears beside the dependent voltage source and that one is clearly ac.
 
doodle said:
Hmm... but a "+" sign also appears beside the dependent voltage source and that one is clearly ac.
Haha! Yes, it does. What on Earth is it for, then?
 
For the dependent voltage source, I would imagine that it is there to indicate where the +terminal is (neccesary in defining voltage). I don't know why it appears beside the current source.
 

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