# Series R and LC circuit question

1. Jul 25, 2010

### sylak

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

Since I dont have a pic.. I will explain my problem. I have a circuit with 3 terminals x , y and z.
Between x - z I have a resistance , say R,
Between z - y I have an inductor L and then a capacitor C in series.
I apply a square wave input between x and y.

2. Relevant equations

How will the voltage at output look like? and why does it look like it? output terminals being z-y.
3. The attempt at a solution

I already know the answer except I cant understand it. Answer being, Vzy would be discontinuous. So far, I have , at the rising edge of the square wave, an impulse current would be across L, now I dont understand how the capacitor will react. can someone explain it? so how would Vzy be discontinuous?

Last edited: Jul 25, 2010
2. Jul 25, 2010

### vela

Staff Emeritus
The current through an inductor is always continuous, and the voltage across a capacitor is always continuous. Does that help?

3. Jul 31, 2010

### CEL

Since the three elements are in series, the current is the same in all three. Write the equations of voltage as a function of the current for the three elements. The sum of the voltages is the input square wave, or a series of positive and negative steps.
Solve the resulting integral-differential equation, to obtain the current in the circuit.
Having the current, you have the voltages in the inductor and capacitor.