Physics - Magnetism Question with Solution | TestHub

currents in$\text{ABC}$and$\text{ADC}$will not be the same because of the resistance and$\text{B}$also depends on length .


$\begin{array}{l}{i}_1=\frac{1}{6}\times 1=\frac{1}{6}A\\ \\ i_2=\frac{5}{6}\times 1=\frac{5}{6}A\\ \\ B_{ABC}=\frac{{\mu }_0{i}_1}{4\pi r}=\frac{{\mu }_0}{4\pi r}\left(\frac{1}{6}\right)\left(\frac{15}{9}\pi \right)\\ \\ B_{ADC}=\frac{{\mu }_0{i}_2}{4\pi r}=\frac{{\mu }_0}{4\pi }\left(\frac{5}{6}\right)\left(\frac{\pi }{3}\right) \end{array}$

equal and opposite magnetic field due to arc$\text{ABC}$&$\text{ADC}$, so net magnetic field at$\text{O}$is zero.