# Homework Help: Circuit Voltage Dynamic Equations

1. Feb 23, 2013

### wilsondd

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

As part of a larger problem, I'm trying to understand the dynamic equations of the attached circuit with two capacitors and one resistor and a voltage source. When I use Kirchoff's Current Law at nodes V0 and V1, I get the following equations.

2. Relevant equations

See Attachment for circuit diagram

3. The attempt at a solution

When I use Kirchoff's Current Law at nodes V0 and V1, I get the following equations.

0 = (dVs/dt-dV1/dt)*C1 - (V1-V2)/R - (dV1/dt-dV2/dt)*C2
0 = (dV1/dt-dV2/dt)*C2 + (V1-V2)/R

I have a feeling that this approach is wrong though, since I can't solve the equation when C1 = C2. I would be very appreciative if someone could tell me where I'm going wrong.

#### Attached Files:

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2. Feb 23, 2013

### Staff: Mentor

If the terminals at V1 are open circuited as shown then no current can flow, so no potential drops will occur...

3. Feb 23, 2013

### wilsondd

Yes, but what if the voltage source is not constant?

4. Feb 23, 2013

### Staff: Mentor

No current can flow. But that doesn't mean the potential cannot change. Anything connected to the top lead of Vs will vary identically in potential w.r.t. to the bottom lead of Vs.