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

Hello all. First time posting so excuse any fourm faux pas I may make. I was wondering if anyone could lend some help with the circuit below (ignore the *, they are just space holders to prevent reformatting of the circuit):

|------) |-----) |--------\/\/\/\/\----------|

|*****C*****C*********R**********|

|********************************|

|--------------------/*** -----------------|

****************Switch

Here are the details of my question:

C1=C2=C (value unknown, used as the energy source, and both charged to 2.5V initially)

R=500 Ohms

Question: Find the minimum value of capacitance such that when the switch is closed at t0 = 0 to t=1ms, the voltage across the resistor (R) does not drop below 4.9 Volts. Please show/explain equations and work.

2. Relevant equations

3. The attempt at a solution

Below is what I have (let me know if any of it is wrong):

Kirchhoff Voltage Law

- v_c - v_c = v_r

2 * v_c = v_r

Inserting voltage equations for v_c and v_r

2 * ( 1/C * Integrate( i_c(t) dt, t0, t) + v_c0 ) = i_r(t) * R

Series circuit so i_c(t) = i_r(t) = i(t)

2 * ( 1/C * Integrate( i(t) dt, t0, t) + v_c0 ) = i(t) * R

Now I'm stuck; how can I express i(t) as a function of knowns and/or C.

Thanks again for all the help!!!

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# Homework Help: Electrical Engineering- Capacitor Resistor Circuit

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