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MHT CET · Physics · Alternating Current

Resistor of \(2 \Omega\), inductor of \(100 \mu \mathrm{H}\) and capacitor of \(400 \mathrm{pF}\) are connected in series across a source of \(\mathrm{e}_{\mathrm{rms}}=0.1\) Volt. At resonance, voltage drop across inductor is

  1. A \(25 \mathrm{~V}\)
  2. B \(2.5 \mathrm{~V}\)
  3. C \(250 \mathrm{~V}\)
  4. D \(20 \mathrm{~V}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(25 \mathrm{~V}\)

Step-by-step Solution

Detailed explanation

At resonance condition,
\(
\mathrm{X}_{\mathrm{C}}=\mathrm{X}_{\mathrm{L}}
\)
The impedance is given as:
\(
\begin{aligned}
& \mathrm{Z}=\sqrt{\mathrm{R}^2+\left(\mathrm{X}_{\mathrm{L}}-\mathrm{X}_{\mathrm{C}}\right)^2} \\
& \mathrm{Z}=\mathrm{R}=2 \Omega \\
& \mathrm{I}_{\mathrm{rms}}=\frac{\mathrm{e}_{\mathrm{mms}}}{\mathrm{R}} \\
& \mathrm{I}_{\mathrm{rms}}=\frac{0.1}{2}=0.05 \mathrm{~A} \\
& \omega=\frac{1}{\sqrt{\mathrm{LC}}}=\frac{1}{\sqrt{10^{-4} \times 4 \times 10^{-10}}} \\
& \omega=5 \times 10^6
\end{aligned}
\)
\(\therefore \quad\) The voltage-drop across the inductor is,
\(
\begin{aligned}
& \mathrm{V}=\mathrm{I}_{\mathrm{rms}} \times \mathrm{X}_{\mathrm{L}}=\mathrm{I}_{\mathrm{rms}} \times \mathrm{L} \omega \\
& \mathrm{V}=0.05 \times 10^{-4} \times 5 \times 10^6 \\
& \mathrm{~V}=25 \mathrm{~V}
\end{aligned}
\)