# Homework Help: Series RLC circuit

1. May 5, 2015

### reddawg

1. The problem statement, all variables and given/known data
Given a series RLC circuit:

R = 10 Ω
L = 0.1 H
C = 2 μF
Power Source: V = 5sin(500t)

If you could change the capacitance what C would you select so Vrms across the capacitor and inductor is zero?

2. Relevant equations
ω2 = 1/LC

3. The attempt at a solution
My instructor's solutions say to use above equation for resonance frequency to input ω=500 (given from V) and
L = 0.1 H and then solve for C, yielding 0.00004 F.

This makes no sense, could someone explain it to me?

2. May 5, 2015

### Svein

Remember: The voltage across the inductance is 180° out of phase with respect to the voltage across the capacitor (jωL vs. 1/[jωC]).

3. May 5, 2015

### reddawg

Ok, I think I get it.

Given a phaser representation, tan(φ) = (XL - XC) / R

So tan(180) = 0 ⇒ XL = XC which is resonance.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted