Circuit/capicator/resistor problem

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Homework Help Overview

The discussion revolves around a circuit problem involving a capacitor and resistors, where the capacitor has been fully charged and the task is to find the steady-state current in each resistor and the charge on the capacitor. The circuit parameters include resistances and a voltage source.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the implications of the capacitor being fully charged, leading to the treatment of its branch as an open circuit. There are attempts to simplify the circuit and clarify the relationships between the resistors.

Discussion Status

Some participants have provided hints and guidance regarding the behavior of the circuit when the capacitor is fully charged, including the effect on the current through the resistors. There is an acknowledgment of correct answers for the current through the resistors, while questions remain about calculating the charge on the capacitor.

Contextual Notes

Participants are navigating the implications of the circuit configuration and the behavior of the capacitor at steady state, with some uncertainty about the application of formulas for charge and voltage across the components.

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Homework Statement



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In the figure below, suppose that the switch has been closed for a length of time sufficiently long enough for the capacitor to become fully charged. (R = 11.0 k, R2 = 15.0 k, R3 = 3.00 k, ΔV = 9.30 V)

Find the steady-state current in each resistor.

Find the charge on the capacitor.


Homework Equations



V=IR
Series/Parallel resistor equations.
C=Q/V

The Attempt at a Solution



I believe you have to use the loop rule but I can't figure out how to simplify the circuit, or even what to do after that. Please help!
 

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When the capacitor is fully charged, current stops flowing into it, so you can treat its branch as an open circuit. See if that gives you a hint about the next step. How does that affect the resistor that's in series with it? What simplifictions will then become possible?
 
So the current in the resistor that is in series with the capacitor would be zero. Which would mean that the current in the other two resistors should be equal to each other, correct? Which would also mean the other two resistors are in series if I'm not mistaken.
 
ok I got the correct answer for the current through the resistors problem! Thanks a lot.
 
Wouldn't the second part of this question (What is the charge on the capacitor?) just be Q=CV? I can't get the correct answer from that though...
 
Correct, R and R2 will be in series after the current in the R3 branch decays to zero. After R3 has no current, next step, what is the voltage across R3? Using that fact, how does the voltage across the capacitor compare to the voltage across R2: would it be smaller or greater or equal? Finally, will the full voltage source V be applied across R, or will the full voltage source be applied across R2, or will V be divided somehow between R and R2? You have to get the capacitor voltage right before you can apply Q=CV.
 
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