Circuit with an uncharged capacitor - desperate

In summary, the current through resistor 2 is not used to charge the capacitor because the potential difference between the battery and the capacitor is too small.
  • #1
erinec
31
0
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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  • #2


For the time being forget R2.
Close the switch .What happens?
 
  • #3


You need another equation for the capacitor.

[tex]i = C \frac{dv}{dt}[/tex]
 
  • #4


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. ^^
 

Related to Circuit with an uncharged capacitor - desperate

1. What is a circuit with an uncharged capacitor?

A circuit with an uncharged capacitor is a circuit in which the capacitor has no stored charge. This can happen when the capacitor is first connected to the circuit or when the circuit has been turned off for a long period of time.

2. How does an uncharged capacitor affect the circuit?

An uncharged capacitor can affect the circuit in several ways. It can cause a temporary high current when first connected, which can damage components. It can also act as an open circuit until it is charged, which can disrupt the flow of current in the circuit.

3. How does an uncharged capacitor become charged?

An uncharged capacitor becomes charged when a voltage is applied across its terminals. This can happen when the circuit is turned on or when an external voltage source is connected to the capacitor.

4. Can an uncharged capacitor be discharged?

Yes, an uncharged capacitor can be discharged by connecting a resistor across its terminals. This allows the stored charge to flow through the resistor and eventually dissipate, leaving the capacitor with no stored charge.

5. What are some potential dangers of an uncharged capacitor in a circuit?

An uncharged capacitor can be dangerous if it is not handled properly. It can cause a high current to flow when first connected, which can damage components or cause electric shocks. It can also store a large amount of energy, which can be released in a dangerous manner if not discharged properly.

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