# R-L-C circuit help!

1. Dec 20, 2009

### SAT2400

1. The problem statement, all variables and given/known data
A 210 ohm resistor in series with 2.9uF capacitor and 390mH inductor are put across a 100Hz ac power supply with a peak-to-peak terminal voltage of 40.0V.
a) What 's the maximum source voltage?
b) Compute the power factor

2. Relevant equations
tantheta= (Vl-Vc)/Vr
cos(phase angle)??

3. The attempt at a solution

a) 20V = answer...I put 40V..why is it 20V??

b) how do I compute the power factor? what does it mean??

2. Dec 20, 2009

### ideasrule

The peak-to-peak voltage is, as the name implies, the difference between the highest and lowest possible voltages. The amplitude of the voltage is (by definition) half of this distance, thus 20 V.

For b, if you don't know what the power factor is, you should really consult your textbook or a reliable website. It's a crucial concept that can't be explained in a few lines.

3. Dec 20, 2009

### SAT2400

for the power factor, I did cos(-57) and got the right answer...
but why is it -57?? which is the phase angle??