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Question: Answered & Verified by Expert
In a LCR circuit capacitance is changed from $C$ to $2 C$. For the resonant frequency to remain unchanged, the inductance should be changed from $L$ to
PhysicsAlternating CurrentJEE MainJEE Main 2004
Options:
  • A
    $4 \mathrm{~L}$
  • B
    $2 \mathrm{~L}$
  • C
    L/2
  • D
    L/4
Solution:
1139 Upvotes Verified Answer
The correct answer is:
L/2
$$
\omega_{\text {res }}=\frac{1}{\sqrt{L C}}
$$
if $\omega_{\text {res }}$ is to remain same, the product LC should also not change.
$$
\begin{aligned}
& \Rightarrow \mathrm{LC}=\mathrm{L}^{\prime} \mathrm{C}^{\prime} \\
& \Rightarrow \mathrm{LC}=\mathrm{L}^{\prime} 2 \mathrm{C} \\
& \Rightarrow \mathrm{L}^{\prime}=\mathrm{L}^2 2
\end{aligned}
$$

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