# Finding the time constant of an inductor

1. Oct 7, 2012

### Jd303

Find the time constant τ for the first order response of the circuit below at t > 0 s.
L = 6 H
R1 = 8 Ω : R2 = 6 Ω

I am really struggling on where even to begin with this question.

I know that for a simplified circuit t = L/R

And that you are meant to analyse the circuit just before and after the switch is closed or something along those lines, but I cant seem to apply it.

Any help to allow me to understand this type of question better would be greatly appreciated. Thanks!

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2. Oct 7, 2012

### Lancelot59

Yes, you break the problem up into two parts. First, start with the switch closed (when t<0). Remember, an inductor supplied by a direct current acts just like a wire. Start by finding the current through the various circuit elements at that time.

3. Oct 7, 2012

### Staff: Mentor

The question just wants you to find the time constant for the circuit for t > 0. So draw the circuit that remains when the switch is open. Trim off any components where current cannot flow. What's the time constant for what remains?