A conducting circular loop of radiius $r$ carries a constant current $i$. It is placed in a uniform magnetic field ${\vec{B}}_0$ such that ${\vec{B}}_0$ is perpendicular to the plane of the loop . The magnetic force acting on the loop is

Answer: CSolution: The magnetic field is perpendicular to the plane of the paper . Let us consider two diametrically opposite elements . By flemin's left hand rule , on element $AB$ the direction of force will be leftwards and the magnitude will be
$dF=I\left(dl\right)B\sin 90\circ =I\left(dl\right)B$
on element $CD$ , the direction of force will be towards right on the plane of the paper and the magnitude will be
$dF=I\left(dl\right)B$.