# 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
51
0
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....

• ###### circuit.JPG
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2. ### kubeek AAC Fanatic!

Sep 20, 2005
4,689
806
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.