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Alternating Current question

2022 · 29 Jul · Shift 2 · Q69
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  5. /2022 · 29 Jul · Shift 2 · Q69

Alternating Current question

2022 · 29 Jul · Shift 2 · Q69

JEE MainPhysicsAlternating CurrentNumerical+4 / −1
A capacitor of capacitance 500 μ\muμ F is charged completely using a dc supply of 100 V. It is now connected to an inductor of inductance 50 mH to form an LC circuit. The maximum current in LC circuit will be ‾\underline{\hspace{2cm}}​ A.
Numerical answer
View written solutionFree

Correct answer: 10

  1. Given data

    • Capacitance: C=500 μF=500×10−6F=5×10−4FC = 500\,\mu F = 500 \times 10^{-6} F = 5 \times 10^{-4} FC=500μF=500×10−6F=5×10−4F
    • Inductance: L=50 mH=50×10−3H=5×10−2HL = 50\,mH = 50 \times 10^{-3} H = 5 \times 10^{-2} HL=50mH=50×10−3H=5×10−2H
    • Initial charging voltage: V=100 VV = 100\,VV=100V
  2. Concept used

    In an ideal LC circuit, the initial energy stored in the charged capacitor is completely transferred to the inductor when the current becomes maximum.

    • Energy initially in capacitor: UC=12CV2U_C = \frac{1}{2}CV^2UC​=21​CV2
    • Energy in inductor at maximum current: UL=12LImax⁡2U_L = \frac{1}{2}LI_{\max}^2UL​=21​LImax2​

    At maximum current, 12CV2=12LImax⁡2\frac{1}{2}CV^2 = \frac{1}{2}LI_{\max}^221​CV2=21​LImax2​

  3. Solve for maximum current

    Cancelling 12\frac{1}{2}21​ from both sides: CV2=LImax⁡2CV^2 = LI_{\max}^2CV2=LImax2​

    So, Imax⁡=VCLI_{\max} = V\sqrt{\frac{C}{L}}Imax​=VLC​​

  4. Substitute values

    Imax⁡=1005×10−45×10−2I_{\max} = 100\sqrt{\frac{5 \times 10^{-4}}{5 \times 10^{-2}}}Imax​=1005×10−25×10−4​​

    Imax⁡=10010−2I_{\max} = 100\sqrt{10^{-2}}Imax​=10010−2​

    Imax⁡=100×10−1=10 AI_{\max} = 100 \times 10^{-1} = 10\,AImax​=100×10−1=10A

  5. Final answer 10\boxed{10}10​

  6. Comparison with stored answer

    Stored correct answer = 101010

    Our derived answer = 101010

    Hence, they agree.

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