# RLC Series Circuit

1. Jun 30, 2008

### jayhar

Given that R = 1 kOhms, L=100mH and C = 1uF, calculate the frequency at which the current in the circuit lags the supply voltage by 45deg.

Show how the impedance of the circuit is given by Z = sqr root R2 + (wL - 1/wC)2
arctan [(wL - 1/wC) / R]

I have not been given any information regarding supply voltages or frequencies.
I can not see how i can calculate impedance with no frequencies.

I am assuming for Q1 that tan theta = XL-XC/R, this can only be 1000/1000 = 1 = 45deg.

2. Jul 4, 2008

### CEL

You already have that $$X_L - X_C = 1000$$
Write the impedances as functions of L and C (known) and the frequency (unknown).
You have one equation with one unknown, so you can calculate it.
Use the calculated frequency to obtain the impedance.