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12th Class Physics Electro Magnetic Induction Question Bank MCQ - Electromagnetic Induction

  • question_answer
    In an inductor of self inductance L = 2 mH, current changes with time according to relation, \[l={{t}^{2}}{{e}^{-t}}\]. At what time emf is zero.

    A) 4s                    

    B) 3s      

    C) 2s                                

    D) 1s

    Correct Answer: C

    Solution :

    (c) 2s                         \[L=2\,mH=2\times {{10}^{-3}}H\]                         \[l={{t}^{2}}{{e}^{-t}}\]             \[\Rightarrow \frac{dl}{dt}={{t}^{2}}{{e}^{-t}}(-1)+{{e}^{-t}}(2t)=t{{e}^{-t}}(-t+2)\]             emf \[\varepsilon =L\frac{dl}{dt}=2\times {{10}^{-3}}\times t{{e}^{-t}}(-t+2)\] Now,  emf = 0, when \[(-t+2)=0\] or \[t=2s\].


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