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JEE Advanced 2017Paper 1
Exam
JEE Advanced
Year
2017
Paper
Paper 1
Subject
Physics
Chapter
Alternating Current

JEE Advanced 2017 · Paper 1 · Physics · Alternating Current

In the circuit shown, L = 1 , C = 1 = 1kΩ . They are connected in...

In the circuit shown, L=1\muH,C=1\muFandR=1kΩ.L = 1\text{\mu}H, C = 1\text{\mu}FandR = 1kΩ . They are connected in series with an a.c. source V=V0sin\omegatV = {V}_{0}sin \text{\omega}t as shown. Which of the following options is/are correct?
In the circuit shown, L = 1 , C = 1 = 1kΩ . They are connected in series with an a.c. source V = V _ 0 sin as shown.

Options

  1. AAt ω≫106radsec−1\omega ≫ {10}^{6}rad{sec}^{- 1} the circuit behaves as a capacitor
  2. BThe frequency at which the current will be in phase with the voltage is independent of RR
  3. CThe current will be in phase with the voltage if ω=104radsec−1\omega = {10}^{4}rad{sec}^{- 1}
  4. DAt ω ~ 0 the current flowing through the circuit becomes nearly zero

Correct answer

B. The frequency at which the current will be in phase with the voltage is independent of RR

Step-by-step solution

The current will be in phase with voltage when phase angle is zero,

∴tanϕ=\omegaL−1\omegaCR=0∴ tan \text{ϕ} = \dfrac{\text{\omega}L - \dfrac{1}{\text{\omega}C}}{R} = 0

Where \omega,L,C,R\text{\omega}, L, C, R are the angular frequency, inductance, capacitance and resistance respectively.

⇒\omega=\omega0=1LC⇒ \text{\omega} = {\text{\omega}}_{0} = \dfrac{1}{\sqrt{LC}}

⇒\omegaο⇒ {\text{\omega}}_{\text{ο}}is independent of RR

⇒(resonantfrequency)\omega0=106rad/s⇒ ( resonantfrequency ) {\text{\omega}}_{0} = {10}^{6}rad / s

Current in the circuit is given by,

i0=V0R2+(\omegaL−1\omegaC)2{i}_{0} = \dfrac{{V}_{0}}{\sqrt{{R}^{2} + {\left(\text{\omega}L - \dfrac{1}{\text{\omega}C}\right)}^{2}}}

When \omega→0,i0→0\text{\omega} \to 0, {i}_{0} \to 0

For \omega≫\omega0\text{\omega} ≫ {\text{\omega}}_{0} circuit behaves as inductor.

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