(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

How much resistance must be added to a pure LC circuit (L = 340 mH, C = 2200 pF) to change the oscillator's frequency by 0.10 percent?

Will the frequency be increased or decreased?

2. Relevant equations

I'm assuming critical damping: R^2=4L/C, w=((1/LC)-R^2/(4L^2))^1/2

With no R: w=(1/(LC))^1/2

3. The attempt at a solution

I've been at this for a few hours :/ I'm letting w stand in for frequency since w=2pif the percent change needed for f should be the same for w (I hope). I've tried several approaches:

First, I tried w=(1/LC)^1/2 to get w. Then multiplied w by .001 to get .1%. Then made an equation: w-((1/LC)-R^2/(4L^2))^1/2=.001w

That didn't work, but the answer was close to the given one.

I also tried simply setting .001w=(1/LC-R^2/2l^2)^1/2 and that answer was further off.

If I'm missing anything or you need information I'd be happy to give it I'm really enthusiastic to get this done. Thank you in advance!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: LRC Circuit: Frequency of Oscillation determined by R

**Physics Forums | Science Articles, Homework Help, Discussion**