• # question_answer 47) A straight section $PO$ of a circuit lies along the x-axis from $x=-a/2$to $x=+a/2,$and carries a steady current 'T'. The magnitude of magnetic field due to the section PO at a point to $y=+a$ will be A)  Proportional to a      B)  Proportional to a2C)  Proportional to I/a     D)  Equal to zero

$B=\frac{{{\mu }_{0}}}{4\pi }\frac{I}{a}(\sin \theta +\sin \theta )=\frac{{{\mu }_{0}}I\sin \theta }{2\pi a}$B at any point on Y axis is inversely proportional to a.