# Can you work out the value of the resistor?

Discuss Can you work out the value of the resistor? in the Electrical Forum area at ElectriciansForums.net

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T

Hi guys,

Just wondering if you can help me on this one,

I have a RLC series circuit the values are as below;

R = unknown
L = 800mH
C = 300uF

from there I have calculated;

the resonant frequency to be 10.3Hz
the capacitive reactance 51.50 ohms

The reason I need to know is I need to work out the impedance, which is

Z= sqrt^R^2+(Xl-Xc)^2

So I have the following,

R is unknown
L is 800mH
C is 300uF
F = 10.3Hz
W = 2pie*F
Xc = 1/WC
Xl = WC

So If there is a way i could work out what the resistors value is, then I can work out what the impedance is, but please bear in mind this is just a paper exercise, so I have no tools i can use to determine this for me.

Tom

#### Marvo

Staff member
If you're currently on a training course you can get access to our Trainee section which you might find helpful.

Check out this thread, do the necessary and access will be granted if you qualify.

#### Lucien Nunes

Respected Member
You have too many unknowns. If you knew the resistor value you could calculate the impedance at a given frequency, or vice versa, but at the moment you have neither so cannot calculate anything.

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#### happysteve

Electrician's Arms
Do you know the Q factor of the resonant circuit? If so, you could work out R using:

Q = (2 x pi x f0 x L) / R

... or ...

Q = 1 / (2 x pi x f0 x C x R)

(where f0 is your resonant frequency)

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