A) 4 s
B) 3 s
C) 2 s
D) 1 s
Correct Answer: C
Solution :
Key Idea: The emf is given by the relation \[e=-L\frac{dt}{dt}.\] It is given that emf is zero i.e., \[e=-L\,\frac{di}{dt}=0\] \[orL\,\frac{di}{dt}=0\] \[or\frac{d}{dt}({{t}^{2}}{{e}^{-t}})=0\] \[or2t\times {{e}^{-t}}+{{t}^{2}}+(-1)\,{{e}^{-t}}=0\] \[ort{{e}^{-t}}(2-t)=0\] \[ort=2\,s\,(\because \,t{{e}^{-t}}\ne 0)\]You need to login to perform this action.
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