8. So, using Ampere's law, we have the left-side of the equation: $\oint \vec{B} \cdot d\vec{l} = \mu_0 I_{enclosed}$.
1. Now, we simply need the right-hand side. If n is the number of loops per meter, explain why the current
enclosed is $I_{enclosed} = n l_1 I$.
2. Then, using that, explain why the magnitude of the field inside a long solenoid (where the field is essentially
uniform), is $B = \mu_0 n I$.