Circuit with an uncharged capacitor - desperate

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Homework Help Overview

The discussion revolves around a circuit involving an uncharged capacitor and the behavior of current and potential across various components when a switch is closed and then reopened. The subject area is primarily focused on circuit analysis and capacitor behavior in electrical circuits.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand why current does not flow through Resistor 2 immediately after the switch is closed, despite the presence of a potential difference from the battery. Some participants suggest focusing on the capacitor's behavior and the implications of closing the switch.

Discussion Status

The discussion is ongoing, with participants exploring the role of the capacitor and questioning the assumptions about current flow in the circuit. Some guidance has been offered regarding the need for additional equations related to capacitors, but no consensus has been reached on the specific behavior of the circuit components.

Contextual Notes

The original poster expresses confusion about the role of Resistor 2 and the charging process of the capacitor, indicating a lack of clarity on how current behaves in this circuit configuration. There is also mention of the fundamental behavior of charge carriers in relation to the capacitor.

erinec
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circuit with an uncharged capacitor -- desperate

Homework Statement


http://img91.imageshack.us/img91/7533/physicsimage.gif
Switch S has been open for a long time. It is closed suddenly at t=0.
A long time later, it is opened.
Determine the potential across and the current through each component at the following times.

Immediately after S closes. <-- one i don't understand...
A long time after S closes.
Immediately after S is reopened.

Homework Equations


Q=CV

The Attempt at a Solution


So immediately after S closes, the capacitor charge is neutral, right? (Since it is uncharged.) The solution says that the current will not go through Resister 2.
So I do not understand why the current will not go through Resistor 2 and go through Capacitor instead.
I thought current charges cannot jump to the other side of the capacitor...There is potential difference between battery, so I thought the current will try to go through resister 2 due to the emf of the battery...
But that is not the case.

I am wondering why all currents going to R2 and C is used to charge the capacitor...
and i also do not understand why that results in no current through R2...

Thank you SO much in advance.

I am sso stuck and very desperate...

If you cannot answer all my questions, my biggest most important question is... Why does current NOT go through R2?

Again, thanks so much for your time.
 
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For the time being forget R2.
Close the switch .What happens?
 


You need another equation for the capacitor.

i = C \frac{dv}{dt}
 


rl.bhat said:
For the time being forget R2.
Close the switch .What happens?

If there is no R2, then the battery charges the capacitor.
Btw, that raises another question.
Since electrons are the charge carriers and electrons cannot ever travel to positive side of the capacitor, does the resistor 1 connected to the positive plate of the capacitor play a role? I am so confused. Thanks for your help.@Phrak:
Thank you so much for your response. I am wondering if you could elaborate a little more. ^^
 

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