# Simple Time Constants

1. Apr 18, 2010

### jayz618

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

Calculate the time constants of the following circuits

I drew them in the attachment

2. Relevant equations

t=RC in a RC Circuit

t= L/R in a RL Circuit

3. The attempt at a solution

Im not sure if in the first one, I would simply add the two resistors and multiply the total by the Capacitance ?

If so, then it would be 45 k Ohm x 2 Micro Farads = 45000 Ohms x 2E-6 Farads = .09 Seconds

The second one, I calculated the value of the parralell resistors as 30 ohm x 80 ohm / 110 ohm = 21.81 Ohms

Then it would just be 50 milliHenries = .05 Henries / 21.81 Ohm = .0022 Seconds

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2. Apr 18, 2010

### kuruman

Correct.

3. Apr 18, 2010

### jayz618

For the first one, it doesnt matter that the second resistor comes after the capacitor ?

4. Apr 18, 2010

### kuruman

It doesn't matter. The resistors are in series. Whatever charges move through one resistor, have to go through the other.

5. Apr 18, 2010

### jayz618

Cool, so I was correct on both attempts ? Good News

Thanks