Question 16.2: Assume an inductor with a negligible resistance is connected......

The first step is to determine the inductive reactance of the circuit:

X_L=\frac{E}{I}

\mathrm{X}_{\mathrm{L}}=\frac{36 \mathrm{~V}}{0.2 \mathrm{~A}}

X_{\mathrm{L}}=180 ~\Omega

Now that the inductive reactance of the inductor is known, the inductance can be determined:

L=\frac{X_L}{2 \pi \mathrm{f}}

L=\frac{180 ~\Omega}{2 \times 3.1416 \times 400 \mathrm{~Hz}}

\mathrm{L}=0.0716~ \mathrm{H}