Physics - Magnetism Question with Solution | TestHub

The magnetic field $B$ due to a long straight conductor carrying current $I$ at a perpendicular distance $x$ is given by

$B=\frac{{\mu }_{0}I}{2\pi x}$

The magnetic field $B^{\prime }$ at a distance $x^{\prime }=\frac{x}{3}$ is

$B^{\prime }=\frac{{\mu }_{0}I}{2\pi \left(\frac{x}{3}\right)}$

$B^{\prime }=3\left(\frac{{\mu }_{0}I}{2\pi x}\right)$

$B^{\prime }=3B$

Answer: 3 B