Question 30 of 153

A coil of inductance $2H$ having negligible resistance is connected to a source of supply whose voltage is given by $V=3t$ volt. (where $t$ is in second). If the voltage is applied when $t=0$, then the energy stored in the coil after $4s$ in $J$,

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Answer: 144

$\epsilon =\dfrac{LdI}{dt}$
$3{\int }_{0}^{4}tdt=2{\int }_{0}^{1}dI$
$\dfrac{3}{2}\times 16=2I$
$I=12$
$V=\dfrac{1}{2}L{I}^{2}=\dfrac{1}{2}\times 2{\left(12\right)}^{2}=144J$