# Parallel and series RLC circuits

Suppose I have a scheme defined by the following equation:

\begin{align} z = \frac 1 {\frac1 {4R} - j* \frac {1}{wL}} - {j*\frac1{wC}}\end{align}

I need to find a vector diagramm of the scheme, which show the phase angle between current and voltage.

• You are dealing with math here, no electronics. Just derive the expression in z=x+j*y then phase is phase=atan(y/x). – Bip Jun 7 '15 at 22:09
• But what if I need to draw a diagramm? How would it look like? How can it be done without finding the phase angle? – JHFVM Jun 7 '15 at 22:11
• You will have imaginary part on y axis, and real on x axis. The angle is then angle between drawn vertex and x axis. You cannot expect someone to do the homework for you! – Bip Jun 7 '15 at 22:15
• It is not homework. I am trying to connect the dots. – JHFVM Jun 7 '15 at 22:19
• Show the schematic to match the formula. – Andy aka Aug 15 '15 at 22:54

## 1 Answer

Since the R and L are in parallel to begin with the voltage across them is going to be the same

1. start by taking the voltage across the parallel branch as your reference.
2. Ir is going to be in phase with your reference and Il is going to lag it by 90 degrees.
3. Then the capacitor is in series with the parallel branch to vectorially add Ir and Il. That will give you Ic.
4. Vc will simply lag Ic by 90 degrees.

That is the general procedure, you can find the Magnitudes by simply applying ohm's law.

• I followed the steps, but somehow I came to the wrong angle. Do not know why. – JHFVM Jun 8 '15 at 1:31
• if you could post the steps then we can help you... – Sada93 Jun 8 '15 at 1:33