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  • An L – C circuit contains a 20 mH inductor and a 50  capacitor with an initial

An L – C circuit contains a 20 mH inductor and a 50 \mu \mathrm{F} capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. At the instant the circuit is closed be t = 0. At what time is the energy stored completely magnetic:

Option: 1

t = 0


Option: 2

t = 1.54 ms


Option: 3

t = 3.14 ms


Option: 4

t = 6.28 ms


Answers (1)

best_answer

For \mathrm{\mathrm{L}-\mathrm{C}, oscillator, \mathrm{T}=2 \pi \sqrt{\mathrm{LC}}}
Fro one extreme to another - when electric field is maximum magnetic field is zero. When electric field is zero, magnetic field is maximum.
At time t= \mathrm{\frac{T}{4}}, energy stored is completely magnetic
\mathrm{\begin{aligned} & \therefore \quad \text { Time, } \mathrm{t}=\frac{\mathrm{T}}{4}=\frac{2 \pi \sqrt{\mathrm{LC}}}{4} \\ & \Rightarrow \mathrm{t}=\frac{\pi \sqrt{20 \times 10^{-3} \times 50 \times 10^{-6}}}{2}=\frac{\pi \sqrt{1 \times 10^{-6}}}{2} \\ & \Rightarrow \mathrm{t}=1.57 \mathrm{~ms} \end{aligned} }

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vinayak

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