# Average power used by circuit?

1. Mar 9, 2009

### icyspicy

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

If the rms voltage across the generator is 149 V, calculate the average power P(at 402 Hz) being used by the circuit.

R = 298 Ω, a capacitance C = 4.1 μF, inductance of L = 0.23 H

https://tycho-s.physics.wisc.edu/cgi/courses/shell/common/showme.pl?courses/phys104/spring09/homework/07/rclseries/ex2s92p4.gif [Broken]

2. Relevant equations

V=IR
Avg power=Vrms*Irms(cos phase angle)
vrms=vmax/(sqrt 2)
Irms=Imax/(sqrt 2)

3. The attempt at a solution

Vrms=IrmsR
149/(sqrt 2)=Irms*298 I think that the 149 V given in the problem needs to be divided by 2 to get Vrms? is rms voltage across generator same as max voltage? i'm not exactly sure about that part...anyways I got:
Irms=.35355
Avg power= (.35355)(149/sqrt 2) cos (phase angle)
i solved for XL (581) and XC (96.6), which were both correct. so I got the phase angle to be 58.4 degrees
Avg power= (.35355)(149/sqrt 2) cos (58.4)

I'm not getting the right answer, so maybe my approach was wrong? Any help is appreciated.

Last edited by a moderator: May 4, 2017
2. Mar 9, 2009

### icyspicy

nevermind, got it