Obtain an expression for the current through an Inductor when an AC emf is applied.

An ideal inductor (no internal resistance for the coil) of $20 \mathrm{mH}$ is connected in series with an AC ammeter to an AC source whose emf is given by $e=20\sqrt{2}\sin \left(200t+\pi /3\right) \mathrm{V}$, where t is in seconds. Find the reading of the ammeter (in Ampere).

The instantaneous current and instantaneous voltage across a series circuit containing resistance and inductance are given by

$i=\sqrt{2}\sin \left(100t-\pi /4\right) \mathrm{A}$ and $v=40\left(100t\right) \mathrm{V}$. Calculate the resistance (in $\mathrm{\Omega }$).

An AC circuit contains a resistance $R$, an inductance $L$ and a capacitance $C$ connected in series across an alternator of constant voltage and variable frequency. At resonant frequency. It is found that the inductive reactance, the capacitive reactance and the resistance are equal and the current in the circuit is $i_{°}$. Find the current in the circuit in terms of $i_{°}$ at a frequency twice that of the resonant frequency.