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Homework Help: Finding the time constant of an inductor

  1. Oct 7, 2012 #1
    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
    Give your answer to at least two decimal places, in s.

    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!

    Attached Files:

  2. jcsd
  3. Oct 7, 2012 #2
    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.
  4. Oct 7, 2012 #3


    User Avatar

    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?
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