Impedance of an inductor is twice that of a capacitor at a particular frequency f. If they are connected in series, what is the resonant frequency?
Right Answer is:
√2f
SOLUTION
An inductor’s impedance is twice that of a capacitor at a specific frequency (f).
Both components are connected in series.
We need to find the new resonant frequency.
Impedance relationship
The inductive reactance XL and capacitive reactance XC are related by:
XL = 2XC
Substituting their formulas:
$\omega L = 2 \cdot \frac{1}{\omega C}$
where
$ \omega = 2\pi f $ is the angular frequency.
Step 2: Solve for angular frequency $$ \omega $$
Rearranging the equation:
$\omega^2 L = \frac{2}{C}$
$\omega = \sqrt{\frac{2}{LC}}$
Step 3: Resonant frequency formula
The resonant angular frequency is related to the resonant frequency ($ f_\text{new}$) by:
$\omega = 2\pi f_\text{new}$
Substitute $ \omega = \sqrt{\frac{2}{LC}}$:
$2\pi f_\text{new} = \sqrt{\frac{2}{LC}}$
Solve for $ f_\text{new}$:
$f_\text{new} = \frac{\sqrt{2}}{2\pi \sqrt{LC}}$
Step 4: Compare with the original resonant frequency
The original resonant frequency ($ f_\text{original}$) is given by:
$f_\text{original} = \frac{1}{2\pi \sqrt{LC}}$
Now compare:
$f_\text{new} = \sqrt{2} \cdot f_\text{original}$
The new resonant frequency is:
$f_\text{new} = \sqrt{2}f$