Calculating Average Power LCR series circuit

[steejk]

Hi,

Im trying to calculate the Q-factor of a series LCR circuit.

I am struggling at how to calculate the average power. I want to find it using this formula:

What is the RMS voltage in the formula for - is it across the resistor, or what?

Any help is appreciated thanks.

 

[tiny-tim]

welcome to pf!

hi steejk! welcome to pf!

What is the RMS voltage in the formula for - is it across the resistor, or what?

from the two denominators, Z² = R² + (X_L - X_C)² …

so Z must be the impedance across all three components (R L and C), and so V = IZ is the voltage (potential difference) across all three

(and V = IZ, so V² = I²Z², so V_rms² = I_rms²Z²)

 

[steejk]

hi steejk! welcome to pf!


from the two denominators, Z² = R² + (X_L - X_C)² …

so Z must be the impedance across all three components (R L and C), and so V = IZ is the voltage (potential difference) across all three

(and V = IZ, so V² = I²Z², so V_rms² = I_rms²Z²)

Thanks :)

 

[steejk]

hi steejk! welcome to pf!


from the two denominators, Z² = R² + (X_L - X_C)² …

so Z must be the impedance across all three components (R L and C), and so V = IZ is the voltage (potential difference) across all three

(and V = IZ, so V² = I²Z², so V_rms² = I_rms²Z²)

Can it also be said that P_avg = V_rms(across resistor)/R ?

 

[tiny-tim]

Can it also be said that P_avg = V_rms(across resistor)/R ?

You mean V_rms(across resistor)²/R ?

Yes, the average power across L and C is zero, and the average power across R is V_rmsI_rms(across resistor) = V_rms(across resistor)²/R