Question

A cylindrical long wire of radius R carries a current $I$ uniformly distributed over the cross-sectional area of the wire.The magnetic field at a distance x from the surface inside the wire is

• A. $\frac{{\mu }_{o}I}{2\pi (R-x)}$
• B. $\frac{{\mu }_{o}I}{2\pi x}$
• C. $\frac{{\mu }_{o}I}{2\pi (R+x)}$
• D. None of these

Answer 1

The correct option is D None of these

From centre, $r=(R-x)$

$B=\frac{{\mu }_o}{2\pi }\frac{I}{R^2}r$
$=\frac{{\mu }_o}{2\pi }\frac{I}{R^2}(R-x)$