Calculating the frequency based on LC circuit

In summary, the conversation is about someone building a lightning detector based on a website and calculating the resonant frequency using a 10mH inductor and a 10pF capacitor. However, the calculated frequency of 5Hz is far from the desired range of 200kHz. After further discussion, it is discovered that there were missing brackets and incorrect values used for the SI units, resulting in a corrected resonant frequency of 503.3 kHz.
  • #1
guns
4
0
Hi all,

I am currently building up a lightning detector based on this website: http://www.techlib.com/electronics/lightningnew.htm
as the diagrams shows, the resonance tank included a 10mH inductor and a 10pF capacitor.
As I want to calculate the resonant frequency (using the formula f = 1/2pi*sqrt(LC)), the answer was 5Hz, which is far from the desired range (should be around 200kHz)
is there any mistake in my calculation or concept? Thanks for your help.

Guns
 
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  • #2
How did you get your answer? Did you consider the SI prefixes (milli, pico)?
I think there are brackets missing in your equation.
 
  • #3
mfb,
I did it this way:
1/2pi*sqrt(10^(-3)*10^(-12))
which approxmately equals to 5 Hz.
 
  • #4
Following up on mfb's post, you're missing brackets and are using the wrong values for the SI units:

10 mH = 10*10^(-3) H
10 pF = 10*10^(-12) F

1/(2*pi*sqrt(10*10^(-3)*10*10^(-12))) Hz = 503.3*10^3 Hz = 503.3 kHz
 
  • #5
oh my, silly me.
Thanks mfb and milesyoung!
 

1. How do you calculate the resonant frequency of an LC circuit?

To calculate the resonant frequency of an LC circuit, you can use the formula f = 1 / (2π√(LC)), where f is the frequency, L is the inductance in Henrys, and C is the capacitance in Farads.

2. What is the purpose of calculating the resonant frequency of an LC circuit?

The resonant frequency of an LC circuit is important because it is the frequency at which the circuit will have maximum current flow and minimum impedance. This can be useful in designing filters, amplifiers, and other electronic circuits.

3. How does the inductance and capacitance values affect the resonant frequency of an LC circuit?

The inductance and capacitance values directly affect the resonant frequency of an LC circuit. As the values of inductance and capacitance increase, the resonant frequency decreases. Similarly, as the values decrease, the resonant frequency increases.

4. Can you calculate the resonant frequency of an LC circuit if the inductance and capacitance values are unknown?

It is not possible to calculate the resonant frequency of an LC circuit if the inductance and capacitance values are unknown. However, you can measure the resonant frequency experimentally by varying the frequency of the input signal until the circuit reaches maximum current flow.

5. What happens to the resonant frequency of an LC circuit if the capacitance is decreased while the inductance remains constant?

If the capacitance is decreased while the inductance remains constant, the resonant frequency of the LC circuit will increase. This is because the decrease in capacitance will result in a decrease in the reactance of the capacitor, leading to an increase in the overall reactance of the circuit and thus, an increase in the resonant frequency.

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