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Question: Answered & Verified by Expert
A coil having inductance L and resistance R is connected to a battery of emf ε  at t=0. If t1 and t2 are the time for 90% and 99% completion of the current growth in the circuit, then t1t2 will be-
PhysicsAlternating CurrentJEE Main
Solution:
1854 Upvotes Verified Answer
The correct answer is: 0.5
I=I01-e-tτ

910I0=I01-e-t1τ

⇒   e-t1τ=110

⇒   et1τ=10

⇒   t1=τln10

and 99100I0=I01-e-t2τ

⇒   e-t2τ=1100

⇒   t2=τln100=2τln10

⇒   t1t2=0.5

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