1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

LR circuit analysis

  1. Apr 22, 2014 #1

    utkarshakash

    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data
    Switch S is closed for long time in the figure shown. Find the current i as soon as the switch is opened.


    3. The attempt at a solution

    At t=∞ inductor behaves as closed circuit. So, I can simply replace it with a wire and calculate the current which comes out to be 9A. But I can't understand what will happen when the switch is opened. Will the current die out instantly? Will it be the same as before?
     

    Attached Files:

  2. jcsd
  3. Apr 22, 2014 #2

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    First of all, how did you get 9 A? Is that what you get for the current through the inductor ? (Yes, I assume you're getting this while the switch is still closed.) ... but how did you get that?
     
  4. Apr 23, 2014 #3

    utkarshakash

    User Avatar
    Gold Member

    Sorry. I misunderstood the question. It asks for the current through the inductor. I calculated the current flowing through the battery instead. btw I got the correct answer.
     
  5. Apr 23, 2014 #4

    ehild

    User Avatar
    Homework Helper
    Gold Member

    So what current flows through the inductor?

    The current through the battery ceases immediately when the switch is opened, but the current through the inductor does not. Think of Lenz's Law.
     
  6. Apr 23, 2014 #5

    rude man

    User Avatar
    Homework Helper
    Gold Member



    Can current EVER die out instantly in an inductor? Can current change in an inductor if you don't give it any time to change?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: LR circuit analysis
  1. LR Circuit. (Replies: 1)

  2. LR circuit (Replies: 8)

  3. LR Circuit (Replies: 1)

Loading...