RC Circuit/Node voltage question

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Discussion Overview

The discussion revolves around solving a problem related to an RC circuit, specifically focusing on finding the voltage across node D while the capacitor is charging. Participants are exploring the relationships between various voltages in the circuit, including the capacitor voltage and the voltage across resistors.

Discussion Character

  • Homework-related, Technical explanation, Exploratory

Main Points Raised

  • One participant attempts to derive the voltage across node D by relating it to the capacitor voltage and using voltage division to find the voltage across resistor Rb.
  • Another participant suggests that the current through Rb should be added to the voltage across the capacitor, indicating a potential oversight in the initial reasoning.
  • There is a mention of the expression for Vc(t) being satisfactory, but the application of this in the context of finding Vb is questioned.
  • A participant expresses uncertainty about the correctness of the approach taken to find the voltage at node D.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are differing views on the usefulness of the expressions derived and the steps taken to find the voltage at node D. The discussion remains unresolved with respect to the correct approach.

Contextual Notes

There may be limitations in the assumptions made regarding the relationships between the voltages and the application of Kirchhoff's Voltage Law (KVL). The discussion does not clarify whether all necessary conditions or definitions have been accounted for.

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Homework Statement


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Homework Equations


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The Attempt at a Solution


So you need to find the voltage across node D while the capacitor is charging, so it is going to be related to the voltage of the capacitor, so a function of time, so you need to come up with the equation for Vc(t), which I did. Then you do voltage division to find the voltage of Vb, which would be (Rb/(Ra+Rb))(Vc(t), then to find the voltage on node D you just need to use KVL and add Vb and Vc(t). But this doesn't simplify down to the expression it should be equal to, so there has to be some gap in my reasoning or something.
 

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I (think I) see you work it out in terms of ##V_C## which isn't very useful in this case.
The expression for ##V_C(t)## looks good to me. Now add ##IR_B##
 
BvU said:
I (think I) see you work it out in terms of ##V_C## which isn't very useful in this case.
The expression for ##V_C(t)## looks good to me. Now add ##IR_B##
I have Vb or voltage drop across Rb from (Rb/(Ra+Rb))(Vc(t), and I am adding that to Vc(t), but that isn't correct
 
Oh ?
 

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