# Homework Help: How to approach this RLC circuit question?

1. Aug 18, 2009

### maks4

1. The problem statement, all variables and given/known data

^^I'm sort of lost as to how to approach this question. Should i just find the voltage at node A? Then at B? But what confuses me the most are these time values we need to take into account.

So what would be the best way to approach this question?
Thanks.

2. Aug 18, 2009

### fleem

When the switch is at A, its an RL ckt, and when its at B you have a RLC ckt. Calculate the waveforms for each of those. For the various switch points in time, find where (in time) it is in those waveforms and scale the levels accordingly. for example, the second time the switch switches to B, you know how much current is in the inductor and how much voltage is in the cap, the ratio of those tells you at what point in time of the waveform of that RLC ckt they are. And of course, don't forget the cap holds its charge when the switch is at A.

EDIT: Practically speaking, flipping that switch will waste a little energy, too. But I'm almost sure you are suppose to ignore that here.

Last edited: Aug 18, 2009
3. Aug 19, 2009

### maks4

^^Thanks fleem! That puts things into perspective for me, we usually do these in tutorials so i'll see how it goes there.

And yeah i'm also assuming that we don't consider the small waste in energy when the switch is changed.