• question_answer In a coil having emf of 8 volt is induced for $0.05$ the value of current changes from 2amp to 4amp. What will be the value of coefficient of self induction of the coil? A)  $0.8$ henry               B)  $0.4$ henryC)  $0.2$ henry               D)  none of these

Here: Emf $E=8$volt Time $t=0.05\text{ }sec$. initial current ${{i}_{1}}=2$ amp $\Rightarrow$ final current ${{i}_{2}}=4$ amp From the Faraday's law of electromagnetic induction, the induced emf is given by                         $E=-L\frac{di}{dt}$                 $\Rightarrow$               $S=-L\,\frac{di}{dt}$                 $\Rightarrow$               $L=-8\frac{dt}{di}=-8\frac{dt}{({{i}_{1}}-{{i}_{2}})}$ $=-8\times \frac{0.05}{2-4}=0.2$ henry.