# Charging/discharging capacitor circuit

1. Feb 21, 2010

### Juan Pablo

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

The circuit http://imgur.com/WSd2L. I'm asked to find the current and voltage on the capacitor using diff. eqns. It says that I can assume that the capacitor doesn't have charge at the begining for the charging circuit and the capacitor in the only source of voltage for the discharge circuit.

3. The attempt at a solution

$$V - R \frac{dQ}{dt} = 0$$

For the charge circuit and

$$R\frac{dQ}{dt} + \frac{Q}{C} = 0$$

for the discharge circuit.

I'm not sure If I did this correctly. To get the current I plan to differentiate the charge function I get. For the Voltage maybe Ohm's law? Sorry if this is completely wrong BTW.