# Resonant Frequency

#### HARRYthefrog

Joined Apr 7, 2021
5
I need to find the resonant frequency of a RLC circuit but not sure if i have done it right or not :
so i did

Spec:
50mH
0.01uF
120R
1V dc

1/2pi sqrt 50mH*10^-3*0.01uF*10^-6=7118 Hz (is this right ) ?

#### Ian0

Joined Aug 7, 2020
8,947
I'd agree with that.

#### LvW

Joined Jun 13, 2013
1,683
I need to find the resonant frequency of a RLC circuit but not sure if i have done it right or not :
so i did

Spec:
50mH
0.01uF
120R
1V dc

1/2pi sqrt 50mH*10^-3*0.01uF*10^-6=7118 Hz (is this right ) ?
How do you define "resonance"?
The result depends on the position of the resistor - in series to L or in parallel to L||C ?

#### HARRYthefrog

Joined Apr 7, 2021
5
How do you define "resonance"?
The result depends on the position of the resistor - in series to L or in parallel to L||C ?
i did it by putting everything in series ,the questions that i was given just said RLC so i just put it in series .

#### LvW

Joined Jun 13, 2013
1,683
i did it by putting everything in series ,the questions that i was given just said RLC so i just put it in series .
So - what is the problem? If you know the definition for "resonance" - why not apply this definition?

#### Delta Prime

Joined Nov 15, 2019
1,311
the questions that i was given just said RLC so i just put it in series .
Is this homework?

#### Ian0

Joined Aug 7, 2020
8,947
Does it make any difference? Isn't the resonant frequency the same regardless of the position of R and whether it is series or parallel resonance. It's the Q that changes.

#### LvW

Joined Jun 13, 2013
1,683
Does it make any difference? Isn't the resonant frequency the same regardless of the position of R and whether it is series or parallel resonance. It's the Q that changes.
Yes - it makes a difference. When R is in series to L only (and not to the parallel combination L||C) the resonant point is not simply SQRT(1/LC). The dame applies when L in series to C with R||C.
Try to find the difference while simply applying the definition for resonance.

#### Ian0

Joined Aug 7, 2020
8,947
Yes - it makes a difference. When R is in series to L only (and not to the parallel combination L||C) the resonant point is not simply SQRT(1/LC). The same applies when L in series to C with R||C.
Try to find the difference while simply applying the definition for resonance.
You're correct - I wasn't thinking of resonant circuits quite that advanced!