Pls Help Me with Basic RLC Circuit!

[Iawia]

Hi I am trying to simulate a RLC circuit in Multisim and verify its resonant frequency. Maybe my understanding of the circuit is amiss but from what I understand RLC resonant frequencies exists at 1/\sqrt{LC} ( I even redid the derivation myself to see this). When I plot it in NI's Multisim I do not get the resonant frequency to be 10kHz for RLC values of

R = 100 ohm
L = .1 H
C = 1e-7 F

Instead, I get something like 1.6Khz, which must be wrong. I am inspecting the node before the resistor, or even the node between the cap and inductor which should have the same resonant peak. Please see attached images and circuit.

Thanks for any help in advance.

 

[rumpfy]

You dont have the factor 2*pi in the denominator.
When I have to do this stuff, I take 1/2*pi to be 16 x 10 -2 in the numerator. The denominator is sqrt(10-1 x 10 -7). this gives 10+4 in the numerator.
so; 16 x 10-2 x 10+4 is 16 x 10 +2 which is 1600 Hz.
Hope this helps.

 

[Iawia]

omg. yes you are right rumpf! thanks for that.

 

[crutschow]

The formula you used gives the frequency in Radians per second, of course.

 

[MrAl]

Hi,

As the others have nicely pointed out, the formula 1/sqrt(LC) does not give you what we usually call the frequency F until after you also divide by 2*pi. What it does give you is a frequency, but we usually call that frequency the "angular frequency" and use the lower case greek letter which looks almost like a lower case English "w" and using the symbol editor it is printed as: "ω".

So we have:
w=1/sqrt(LC)

and
f=w/(2*pi)

Most electrical simulators plot the frequency "f" in Hertz, and that is what yours plotted too.