How I find value of U on R2 long time after switch is closed

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Discussion Overview

The discussion revolves around determining the voltage (U) across resistor R2 a long time after a switch in a circuit is closed. Participants explore the behavior of capacitors in the circuit and the implications for current flow through various components, including resistors R1 and R2.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a formula for U based on Kirchhoff's rules and questions its correctness.
  • Some participants suggest that if no current is flowing through the capacitors, then current must flow only through resistors R2 and R1.
  • Another participant challenges the assumption that there is no current through R1, arguing that a current path remains even after the capacitors are charged.
  • A hint is provided suggesting that components with no current can be removed from the circuit, although this is noted as not always being true.

Areas of Agreement / Disagreement

Participants express uncertainty about the behavior of current in the circuit, particularly regarding the flow through R1 and the role of the capacitors. There is no consensus on the correctness of the initial formula or the assumptions made about current flow.

Contextual Notes

Participants have not fully resolved the implications of the capacitors being charged and how this affects current flow through the resistors. There are also differing interpretations of when components can be considered inactive in the circuit.

nisamto
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Thread moved from Electrical Engineering forum, so no template included.
https://qph.is.quoracdn.net/main-qimg-c22d8aa4be4fc2ed9b2f1c7060982e04?convert_to_webp=true
How to find value of U on R2 long time after switch is being closed?

Capacitors are charged so there is no current going through? Or?
I used kirchof rule so i get
Uo+Uc1-U=0
U=Uc1+Uo
U=R2/(R3+R2+(R1R/R1+R))*Uo

Is this correct or?

If not can someone do this example and explain me :)
 
Last edited by a moderator:
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Is this homework? If so, I should be posted on the homework forum.

According to your diagram, if no current is passing through the capacitors, then current flows only through R2 and R1. Can you do the rest?
 
anorlunda said:
Is this homework? If so, I should be posted on the homework forum.

According to your diagram, if no current is passing through the capacitors, then current flows only through R2 and R1. Can you do the rest?
No. How come that there is current through R1?
 
nisamto said:
No. How come that there is current through R1?
Because with the switch closed there continues to be a current path through R1 even after the capacitors have charged.

http://www.imageshack.com/a/img109/4666/holly1756.gif
 
Last edited by a moderator:
Hint: If there is no current flowing through a component it can be removed from the circuit without affecting anything. Try redrawing your circuit with any such components replaced with an open circuit.

Edit: Actually this is not always true but try it anyway.
 

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