1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Problem with inductors and Capacitors in Series (AC Theroy)

  1. Dec 2, 2008 #1
    1. The problem statement, all variables and given/known data

    Find the steady state expresion for i(t) in the circuit if Vs=750 Cos(5000t) mV

    All componets are in series

    Resitor = 400 Ohms
    Inductor = 40mH
    Cap = .4 [tex]\mu[/tex]F

    2. Relevant equations

    Xc= 1/(j*w*C)
    Xl = j*w*L
    Xr = R

    3. The attempt at a solution

    Ok I know how to do most of the problem but, when I look at the teachers solution it throws me off. What I would do is first find the impedences of all of the componets and then add them toghether to find the total. Then divide the voltage by the impedence and viola all done. My dilema is what frequency to use. I started out by using 5000 but, when I look at the teachers solution he used 5. I'm assuming this is because of the mV but, I thought that the frequency is independent from the voltage. It shouldn't matter what units of voltage are there since it's just a scalar. Anyways any help would be apprecieted.

  2. jcsd
  3. Dec 2, 2008 #2
    Nevermind I figured out what he was doing. He was simply droping zeros and moving the decimal points. grrrr stupid mistake.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook