Thank you for reporting, we will resolve it shortly
Q.
A coil of inductance $ 8.4 \,mH $ and resistance $ 6 \, \Omega $ is connected to $ 12\, V $ battery. The current in the coil is $ 1\,A $ at approximately the time
The current-time $(i-t)$ equation in $L-R$ circuit is givcn by (growth of current in $L-R$ circuit)
$i=i_{0}\left(1-e^{-t / \tau_{L}}\right)\, ....(i)$
where,$i_{0} =\frac{V}{R}=\frac{12}{6}=2\, A $
and $\tau_{L} =\frac{L}{R}=\frac{8.4 \times 10^{-3}}{6} $
$ =1.4 \times 10^{-3} s$
and $i=1 \,A$ (given)
Putting the above values in Eq. (i), we get
$t =0.97 \times 10^{-3} \,s $
$=1 \,ms$