image please help me in plz help me in this IES question on circuit theory (subject)

Discussion in 'General Electronics Chat' started by munna007, Jun 30, 2011.

  1. munna007

    Thread Starter Active Member

    Jul 23, 2008
    i m trying to solve this question by method given in most of the standard books i.e.

    Vc(t) = Vc(\infty) - [Vc(0-) - Vc(\infty) ] e ( -t/RC)

    first i found Vc(0-)by considering switch open and inductor behaving like short and capacitor open at steady state....then i find voltage acroos 4 ohm resistor i.e.

    V4 = (4 * 18)/6 = 12 volt

    now =Vc(0-)= [C(total)/2c ] * V4 = 4 volt

    now i m finding [Vc(0-) by considering switch closed ....and at steady state inductor will be shorted and both capacitors will be opened....and now inductor path and capacitor c bot are in parallel and i have confused what to do here next .....please help me....
    Last edited: Jun 30, 2011
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
    When the switch is open, the current through L is 3A. Since an inductor tries to keep the current constant, when you close the switch that current will have to be sourced by C and 2C.

    I would say the current will divide according to the capacitances, so the 2C current should be 2A, but this is getting into the guessing area.