Question

The current through a coil of self inductance L = 2 mH is given by $I=t^2{e}^{–t}$ at time t. How long it will take to make the emf zero?

• A. 1s
• B. 2s
• C. 3s
• D. 4s

Answer 1

The correct option is B 2s

$\epsilon =-L\frac{dI}{dt}=0$
$\Rightarrow \frac{dI}{dt}=0$
$\Rightarrow -t^2{e}^{-1}+e^{-1}2t=0$
or, $e^{-t}(2t-t^2)=0$
or, t=2s