A coil of inductance 300 mH and resistance 2 is connected to a...

The current at any instant is given by $I=I_0\left(1-e^{-R t / L}\right)$$\begin{aligned} \frac{I_0}{2} & =I_0\left(1-e^{-R t / L}\right) \\ \frac{1}{2} & =\left(1-e^{-R t / L}\right) \\ e^{-R t / L} & =1 / 2 \\ \frac{R t}{L} & =\ln 2\end{aligned}$$$<img src="https://cdn-question-pool.Quantrex.app/pyq/jipmer/x6qicJADKOqLL8vhxoGtfK2kEWyVwZHIYSHCfvIPS9I.original.fullsize.png"/>$$\begin{aligned} \therefore \quad t=\frac{L}{R} \ln 2 & =\frac{300 \times 10^{-3}}{2} \times 0.693 \\ & =150 \times 0.693 \times 10^{-3} \\ & =0.10395 \mathrm{~s}=0.1 \mathrm{~s} \end{aligned}$$