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Alternating Current question

2024 · 29 Jan · Shift 1 · Q65
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Alternating Current question

2024 · 29 Jan · Shift 1 · Q65

JEE MainPhysicsAlternating CurrentMCQ+4 / −1
A capacitor of capacitance 100μF100 \mu \mathrm{F}100μF is charged to a potential of 12 V12 \mathrm{~V}12 V and connected to a 6.4 mH6.4 \mathrm{~mH}6.4 mH inductor to produce oscillations. The maximum current in the circuit would be :
  1. A
    2.0 A
  2. B
    3.2 A
  3. C
    1.5 A
  4. D
    1.2 A
View written solutionFree

Correct answer: C

  1. Use conservation of energy in an ideal LC circuit

When the charged capacitor is connected to the inductor, energy oscillates between the capacitor and the inductor.

  • Initial energy stored in capacitor: UC=12CV2U_C = \frac{1}{2}CV^2UC​=21​CV2
  • Maximum energy stored in inductor: UL=12LImax⁡2U_L = \frac{1}{2}LI_{\max}^2UL​=21​LImax2​

At maximum current, all the energy of the capacitor is transferred to the inductor, so 12CV2=12LImax⁡2\frac{1}{2}CV^2 = \frac{1}{2}LI_{\max}^221​CV2=21​LImax2​

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

  1. Substitute the given values

Given: C=100 μF=100×10−6F=10−4FC = 100\,\mu F = 100 \times 10^{-6} F = 10^{-4} FC=100μF=100×10−6F=10−4F L=6.4 mH=6.4×10−3HL = 6.4\,mH = 6.4 \times 10^{-3} HL=6.4mH=6.4×10−3H V=12 VV = 12\,VV=12V

So, Imax⁡=1210−46.4×10−3I_{\max} = 12\sqrt{\frac{10^{-4}}{6.4 \times 10^{-3}}}Imax​=126.4×10−310−4​​

  1. Simplify the expression

10−46.4×10−3=16.4×10−1=0.015625\frac{10^{-4}}{6.4 \times 10^{-3}} = \frac{1}{6.4}\times 10^{-1} = 0.0156256.4×10−310−4​=6.41​×10−1=0.015625

Therefore, Imax⁡=120.015625I_{\max} = 12\sqrt{0.015625}Imax​=120.015625​

Now, 0.015625=0.125\sqrt{0.015625} = 0.1250.015625​=0.125

Hence, Imax⁡=12×0.125=1.5 AI_{\max} = 12 \times 0.125 = 1.5\,AImax​=12×0.125=1.5A

  1. Match with the options

The maximum current is 1.5 A\boxed{1.5\,A}1.5A​

So the correct option is C.

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