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Kirchoff's Law problem

  1. May 11, 2014 #1
    http://i.imgur.com/EFciS60.png

    How do you do part e? Also can someone explain why the current I3 isn't 0 if the switch has been closed for a long time? Doesn't it behave like a short circuit if the switch is closed because the capacitor becomes fully charged and the current becomes zero ish?
     
    Last edited: May 11, 2014
  2. jcsd
  3. May 11, 2014 #2

    phinds

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    2016 Award

    This is simple circuit analysis. You have to show an attempt yourself.

    If the switch has been closed for a long time that current is zero.

    No, it becomes an OPEN circuit and the current is zeor-ish.

    Yes, and you should have shown some attempt at your own work in the homework template.
     
  4. May 11, 2014 #3
    Oh this was from a test, I could have shown it but I got 5.5/10 on it so it wasn't very useful.
     
  5. May 11, 2014 #4
  6. May 11, 2014 #5
    What's the difference? I thought they were the same thing? They both mean the switch is open no?
     
    Last edited: May 11, 2014
  7. May 11, 2014 #6

    phinds

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    2016 Award

    Do you understand that a short circuit and an open circuit are not the same thing? Sloppy terminology results from and/or causes sloppy thinking, so saying that a short circuit and an open circuit are the same thing is not a good idea.
     
  8. May 11, 2014 #7
    Ya no kidding...
     
  9. May 11, 2014 #8
    Do you guys think these answers are correct? I posted the problem to chegg but I have like 3 different answers. I think this one might might be legit, but I don't know if it's really discharging or not. I think it's charging up because it's an open circuit and current is trying to pass through it but it's fully charged. I don't understand what he did for part D so I think that's wrong, but everything else is legit.

    QbAjrXd.png

    (or on imgur)
    http://i.imgur.com/KxAoeQ4.jpg?2
     
    Last edited: May 11, 2014
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