a 100 ohm resistor & 0.8 H inductor is connected in series with an ac source due to which the curent is i=0.7sin(300t + π/6) amp.what is rms voltage across the inductor?

Dear student
Please find below the solution to your asked query.
$$\begin{gathered} I = 0.7\sin (300t+\pi /6) \\ I=I_0=\sin (\omega t+\varphi ) \\ {X}_L = \omega L=0.8\times 300=240 ohm \\ in series current remains the same \\ Peak value of current across inductor=0.7A \\ Peak value of volatge across the inductor \\ {E}_0 = I_0{X}_L=0.7\times 240=168 volt \\ Rms value of emf across the inductor=E_{rms} = \frac{E_0}{\sqrt{2} }=\frac{168}{1.414}=118.81 vollt \end{gathered}$$

Hope this information will clear your doubt about alternating current.
If you have any doubt do ask on the forum our experts will have you out.
Keep Posting!
Regards