Physics - Magnetism Question with Solution | TestHub

The correct option is (C). Concept: Using Ampear's circuital law the magnetic field due to a current carrying wire at a distance $r$ is given by, $B=\frac{{\mu }_{0}I}{2\pi r}$ where, $\mathrm{I}$ is the current through the wire. If the magnetic field due to the wire A cancels out the magnetic field due to the wire $\mathrm{B}$ at the wire $\mathrm{C}$, then $\frac{{\mu }_0{I}_A}{2\pi x}=\frac{{\mu }_0{I}_B}{2\pi (15-x)}$ $\frac{(15-x)}{x}=\frac{I_B}{I_A}$ Therefore, for ${\mathrm{I}}_{\mathrm{B}}=10\mathrm{A}$ and ${\mathrm{I}}_{\mathrm{A}}=15\mathrm{A}$, we get $\mathrm{x}=9\mathrm{cm}$.