Consider a circular current-carrying loop of radius R in the x-y plane with center at the origin. Consider the line integral (L)=LLB.dl taken along the z-axis.

(a) Show that (L) monotonically increases with L.

(b) Use an appropriate Amperian loop to show that (∞) = μ0I, where l is the current in the wire.

(c) Verify directly the above result.

(d) Suppose we replace the circular coil by a square coil of sides R carrying the same current I. What can you say about (L) and (∞)?