Chapter 28, Problem 62GP

For two long parallel wires separated by a distance d, carrying currents I₁ and I₂ as in Fig. 28–10, show directly (Eq. 28–1) that Ampère’s law is valid (but do not use Ampère’s law) for a circular path of radius r (r < d) centered on I₁:

${\displaystyle \oint \stackrel{\to }{B}\cdot d\stackrel{\to }{\mathcal{l}}}={\mu }_0{I}_1.$