RC DC Series and Parallel Circuit

AI Thread Summary
The discussion revolves around solving an RC circuit problem, where the user initially miscalculated the total current. After reevaluating, they correctly determined the current through R2 and calculated the voltage across the resistors and capacitors. A key point raised is that current flows through the capacitors only during the initial connection; once they are fully charged, no current flows. The conversation concludes with the user expressing understanding of the concepts discussed. This highlights the importance of correctly applying Kirchhoff's laws and understanding capacitor behavior in circuits.
DeadFlower
Messages
3
Reaction score
0
Hi!

Homework Statement



attachment.php?attachmentid=61046&stc=1&d=1377062905.jpg

Homework Equations



V = IR
Kirchhoff Current and Voltage Law.

The Attempt at a Solution



I am facing difficulty with this RC circuit.
I tried looking up solutions but all I could find were either exclusively series or parallel.

My first guess was to take Total Current = 28/(6+18). However, that ended up being wrong.
I worked backwards from the answer provided and realized that Current through R2 = 28/(6+18) instead of what I thought earlier. However, I am unable to relate this to any of the formula I can find.I would be a great help if someone were able to explain to me how to arrive and the solutions to the question.
Thanks.
 

Attachments

  • RC DC.JPG
    RC DC.JPG
    14.3 KB · Views: 608
Last edited:
Physics news on Phys.org
DeadFlower said:
Hi!

Homework Statement



attachment.php?attachmentid=61046&stc=1&d=1377062905.jpg



Homework Equations



V = IR
Kirchhoff Current and Voltage Law.


The Attempt at a Solution



I am facing difficulty with this RC circuit.
I tried looking up solutions but all I could find were either exclusively series or parallel.

My first guess was to take Total Current = 28/(6+18). However, that ended up being wrong.

How did you proceed from here?

DeadFlower said:
I worked backwards from the answer provided and realized that Current through R2 = 28/(6+18) instead of what I thought earlier. However, I am unable to relate this to any of the formula I can find.


I would be a great help if someone were able to explain to me how to arrive and the solutions to the question.
Thanks.

Does any current flow through the capacitors after reaching the equilibrium voltage?
The "total current" is the same as the current through either R2 and R1.

ehild
 
Can you calculate the voltages across the capacitors?
 
ehild said:
How did you proceed from here?



Does any current flow through the capacitors after reaching the equilibrium voltage?
The "total current" is the same as the current through either R2 and R1.

ehild

Oh my. It was a mathematical error on my part. I deeply apologise.

After taking Total Current = V/R= 28/(6+18) = 1r1r6 A
Voltage across R1 = IR = 1r1r6 * 6 = 7 V
Therefore voltage across C1 + C2 = 28 - 7 = 21 V
Capacitance total = (1/12 + 1/24)^-1 = 8 μF
Therefore Charge across C1 and C2 = CV = (8*10^-6)(21) = 168 μC (FOUND)

However there is one thing I would like to ask.
So, this means that no current flows through the capacitors?
 
DeadFlower said:
However there is one thing I would like to ask.
So, this means that no current flows through the capacitors?

It flows at the beginning when the circuit is connected. After a while, the capacitors are charged, till the voltage gets the same across them as the voltage across R2. After that, no more potential difference to drive charges to the capacitor plates, so no current flows after the steady state is settled.


ehild
 
ehild said:
It flows at the beginning when the circuit is connected. After a while, the capacitors are charged, till the voltage gets the same across them as the voltage across R2. After that, no more potential difference to drive charges to the capacitor plates, so no current flows after the steady state is settled.


ehild

Ahhh, I understand now. Thanks!

Thread closed then :)
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Correct statement about a reservoir with an outlet pipe'
The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
Back
Top