Correct answer is option d) 0.1 s
Explaination:
During growth of charge in an inductance, I = I_{0} (1 – e ^{–Rt/L})
or \(\frac{I_0}{2} = I_0(1 – e^{ –\frac{Rt}{L}})\)
\( e^{ –\frac{Rt}{L}}=\frac{1}{2}=2^{-1}\)
or \( \frac{Rt}{L} =ln2\)
⇒t = (\(\frac{L}{R}\))In 2
t =[\(\frac{(300 \times 10^{-3})}{2}\)] x (0.693)
or t = 0.1 sec