a
when ${x}<{a}$
${B}_{1}(2 \pi {x})=\mu_{\circ}\left(\frac{{i}_{\circ}}{\pi {a}^{2}}\right) \pi {x}^{2}$
${B}(2 \pi {x})=\frac{\mu_{\circ} {i}_{\circ} {x}^{2}}{{a}^{2}}$
${B}_{1}=\frac{\mu_{\circ} {i}_{\circ} {x}}{2 \pi {a}^{2}}...(1)$
when ${a}<{x}<{b}$
${B}_{2}(2 \pi {x})=\mu_{0} {i}_{0}$
${B}_{2}=\frac{\mu_{{o}} {i}_{\circ}}{2 \pi {x}}...(2)$
$\frac{{B}_{1}}{{B}_{2}}=\frac{\mu_{\circ} {i}_{\circ} \frac{{x}}{2 \pi {a}^{2}}}{\frac{\mu_{\circ} {i}_{\circ}}{2 \pi {x}}}=\frac{{x}^{2}}{{a}^{2}}$
