# RC Circuit

1. Jul 22, 2009

### runfast220

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

Three identical capacitors are connected with a resistor in two different ways. When they are connected as in part A of the drawing, the time constant to charge up this circuit is .34s. What is the time constant when they are connected with the same resistor as in part B?

2. Relevant equations

t = RC

3. The attempt at a solution

I think the first thing I would need to do is find the capacitance of the first circuit, but I don't know how to do that since I only know the time.

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2. Jul 23, 2009

### G01

Can you find an expression for the capacitance, C, using the time constant given?

HINT: Solve for C in terms of $\tau$ using info from circuit A. Then use that expression for C to solve for the time constant in circuit B.

3. Jul 23, 2009

### rl.bhat

Find the equivalent capacitance in the circuit A and B using series and parallel combination formula.
Then write two equations for time constant, one for A and other for B.
From them find the time constant of B

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