Physics - Magnetism Question with Solution | TestHub

Net magnetic field due to loop $ABCD$ at $O$ is $$\begin{array}{rl}& B=B_{AB}+B_{BC}+B_{CD}+B_{DA}\\ & =0+\frac{{\mu }_{o}I}{4\pi a}\times \frac{\pi }{6}+0-\frac{{\mu }_{o}I}{4\pi b}\times \frac{\pi }{6}=\frac{{\mu }_{o}I}{24a}-\frac{{\mu }_{o}I}{24b}=\frac{{\mu }_{o}I}{24ab}(b-a)\end{array}$$