# Homework Help: How I find value of U on R2 long time after switch is closed

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1. Dec 24, 2015

### nisamto

• Thread moved from Electrical Engineering forum, so no template included.
https://qph.is.quoracdn.net/main-qimg-c22d8aa4be4fc2ed9b2f1c7060982e04?convert_to_webp=true [Broken]
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: May 7, 2017
2. Dec 24, 2015

### Staff: Mentor

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?

3. Dec 24, 2015

### nisamto

No. How come that there is current throught R1?

4. Dec 24, 2015

### Staff: Mentor

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 [Broken]

Last edited by a moderator: May 7, 2017
5. Dec 26, 2015

### CWatters

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.