# Energy stored in a capacitor

1. Mar 6, 2011

### zorro

1. The problem statement, all variables and given/known data

Long time after closing K1,k2 and k3 the energy stored in each capacitor is?

3. The attempt at a solution

My method is to find out an expression for the current through the capacitor (of net capacitance 2C) at any time t and use I = CdV/dt to find out V across it at t=inf.

However this method appears to be very long. Is there any shortcut?

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2. Mar 6, 2011

### Antiphon

Yes. At T=inf the current through the capacitors is zero.

3. Mar 6, 2011

### SammyS

Staff Emeritus
Also notice: that will leave you with a fairly simple circuit. The capacitors in combination with R3 are in parallel with R2[/SUB, but the voltage drop across R3 is zero since there is no current through it.

4. Mar 7, 2011

### zorro

So you mean voltage drop across any capacitor is V ?

5. Mar 7, 2011

### SammyS

Staff Emeritus
No.

As t → ∞ :

The only current flowing is through R1 and R2.

What is the voltage drop across R2?

6. Mar 8, 2011

Its V/3
Thank you!!

7. Mar 8, 2011

### SammyS

Staff Emeritus
Correct !