# Homework Help: RLC circuits

1. Oct 4, 2005

### dagg3r

1.
A RLC circuit is used in a radio to tune into an FM broadcasting station at 99.7 Mhz. The resistance in the circuit is 12.0 ohm, and the inductance is 1.40 uH (micro Henry) what capacitance should be used?

this question is tricky what i tried to do is used XC=1/wC where C is capacitance, and w=2*pi*f
and XL=WL i can find Xl since we have the inductance,
but cannot calculate Capacitance since we dont have Xc....
any suggestions?

2. an inductor is connected to a sinusoidal voltage with amplitude of 120V. A peak current of 3.0A appears in the inductor.

a)what is the maximum current if the frequency of the applid voltage is douled
b) what is the inductive reactance at each of the two frequencies?

i have no idea how to do this... i can only think of I = V/R

2. Oct 4, 2005

### Astronuc

Staff Emeritus
One uses an RLC circuit to tune to a frequency - the resonant frequency.

1.) What is the relationship between the resonant frequency f, inductance L, and capacitance C?

2.) Resistance is a type of impedance, and so is inductance.

Think of the relationship between Voltage, Current and Impedance.

3. May 2, 2011

### i_Smash

Hi there, I'm a first year mechatronics student and have come across a problem similar to the OPs question 1.
I have several equations relating to f, L and C but I think the most relevant is: tan(\theta)=((Xl-Xc)/R)
Xl will equal 2*\pi*L but not sure about the tan(\theta) aspect...
Or is it simpler than that and the resistor isn't involved eg, \omega =1/(sqrt(LC))?
M-

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