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Question: Answered & Verified by Expert
A coil of inductance $300 \mathrm{mH}$ and resistance $2 \Omega$ is connected to a source of voltage 2V. The current reaches half of its steady state value in
PhysicsElectromagnetic InductionJEE MainJEE Main 2005
Options:
  • A
    $0.05 \mathrm{~s}$
  • B
    $0.1 \mathrm{~s}$
  • C
    $0.15 \mathrm{~s}$
  • D
    $0.3 \mathrm{~s}$
Solution:
1463 Upvotes Verified Answer
The correct answer is:
$0.1 \mathrm{~s}$
$\mathrm{I}=\mathrm{I}_{\circ}\left(1-\mathrm{e}^{-\frac{\mathrm{R}}{\mathrm{L}}\mathrm{t}}\right)$
$0.693=\frac{\mathrm{R}}{\mathrm{L}} \mathrm{t}$
$\mathrm{t}=\frac{.3 \times 0.693}{2}=0.1 \mathrm{sec}$

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